HUMAN    FOODS 

AND  THEIR  NUTRITIVE  VALUE 


BY 
HARRY   SNYDER,    B.S. 

)  •' 

PROFESSOR   OF  AGRICULTURAL   CHEMISTRY,   UNIVERSITY   OF 

MINNESOTA,   AND    CHEMIST   OF   THE   MINNESOTA 

EXPERIMENT   STATION 


gorfc 

THE   MACMILLAN   COMPANY 
1911 

All  rights  reserved 


COPYRIGHT,  1908, 
BY  THE  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  November,  1908.     Reprinted 
October,  1909  ;  September,  1910  ;  February,  1911. 


NortoooU 

J.  8.  Gushing  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PREFACE 

SINCE  1897  instruction  has  been  given  at  the  Uni- 
versity of  Minnesota,  College  of  Agriculture,  on  human 
foods  and  their  nutritive  value.  With  the  development 
of  the  work,  need  has  been  felt  for  a  text-book  present- 
ing in  concise  form  the  composition  and  physical  prop- 
erties of  foods,  and  discussing  some  of  the  main  factors 
which  affect  their  nutritive  value.  To  meet  the  need, 
this  book  has  been  prepared,  primarily  for  the  author's 
classroom.  It  aims  to  present  some  of  the  principles 
of  human  nutrition  along  with  a  study  of  the  more  com- 
mon articles  of  food.  It  is  believed  that  a  better  under- 
standing of  the  subject  of  nutrition  will  suggest  ways 
in  which  foods  may  be  selected  arid  utilized  more  intel- 
ligently, resulting  not  only  in  pecuniary  saving,  but  also 
in  greater  efficiency  of  physical  and  mental  effort. 

Prominence  is  given  in  this  work  to  those  foods,  as 
flour,  bread,  cereals,  vegetables,  meats,  milk,  dairy 
products,  and  fruits,  that  are  most  extensively  used  in 
the  dietary,  and  to  some  of  the  physical,  chemical,  and 
bacteriological  changes  affecting  digestibility  and  nutri- 
tive value  which  take  place  during  their  preparation 
for  the  table.  Dietary  studies,  comparative  cost  and 
value  of  foods,  rational  feeding  of  men,  and  experiments 


238906 


VI  PREFACE 

and  laboratory  practice  form  features  of  the  work.  Some 
closely  related  topics,  largely  of  a  sanitary  nature,  as 
the  effect  upon  food  of  household  sanitation  and  storage, 
are  also  briefly  discussed.  References  are  given  in 
case  more  extended  information  is  desired  on  some  of 
the  subjects  treated.  While  this-  book  was  prepared 
mainly  for  students  who  have  taken  a  course  in  general 
chemistry,  it  has  been  the  intention  to  present  the  topics 
in  such  a  way  as  to  be  understood  by  the  layman  also. 

This  work  completes  a  series  of  text-books  under- 
taken by  the  author  over  ten  years  ago,  dealing  with 
agricultural  and  industrial  subjects:  "Chemistry  of 
Plant  and  Animal  Life,"  "Dairy  Chemistry,"  "Soils 
and  Fertilizers,"  and  "  Human  Foods  and  their  Nutritive 
Value."  It  has  beefrthe  aim  in  preparing  these  books 
to  avoid  as  far  as  possible  repetition,  but  at  the  same 
time  to  make  each  work  sufficiently  complete  to  permit 
its  use  as  a  text  independent  of  the  series. 

One  of  the  greatest  uses  that  science  can  serve  is  in 
its  application  to  the  household  and  the  everyday  affairs 
of  life.  Too  little  attention  is  generally  bestowed  upon 
the  study  of  foods  in  schools  and  colleges,  and  the 
author  sincerely  hopes  the  time  will  soon  come  when 
more  prominence  will  be  given  to  this  subject,  which 
is  the  oldest,  most  important,  most  neglected,  and  least 
understood  of  any  that  have  a  direct  bearing  upon  the 

welfare  of  man. 

HARRY   SNYDER. 


CONTENTS 

CHAPTER   I 

PAGE 

GENERAL  COMPOSITION  OF  FOODS i 

Water ;  Dry  Matter ;  Variations  in  Weight  of  Foods  ; 
Ash ;  Function  of  Ash  in  Plant  Life ;  Organic  Matter ; 
Products  of  Combustion  of  Organic  Matter ;  Classification 
of  Organic  Compounds  ;  Non-nitrogenous  Compounds  ; 
Carbohydrates  ;  Cellulose ;  Amount  of  Cellulose  in  Foods  ; 
Crude  Fiber;  Starch;  Microscopic  Structure  of  Starch; 
Dextrin ;  Food  Value  of  Starch ;  Sugar ;  Pectose  Sub- 
stances ;  Nitrogen-free-extract ;  Fats  ;  Fuel  Value  of  Fats  ; 
Iodine  Number  of  Fats  ;  Glycerol  Content  of  Fats  ;  Ether 
Extract  and  Crude  Fat;  Organic  Acids;  Dietetic  Value 
of  Organic  Acids  ;  Essential  Oils  ;  Mixed  Compounds  ; 
Nutritive  Value  of  Non-nitrogenous  Compounds  ;  Nitrog- 
enous Compounds  ;  General  Composition  ;  Protein  ;  Sub- 
divisions of  Proteins ;  Crude  Protein ;  Food  Value  of 
Protein  ;  Albuminoids  ;  Amids  and  Amines  ;  Alkaloids  ; 
General  Relationship  of  the  Nitrogenous  Compounds. 

CHAPTER   II 

CHANGES  IN  COMPOSITION  OF  FOODS  DURING  COOKING  AND 

PREPARATION 27 

Raw  and  Cooked  Foods  compared  as  to  Composition ; 
Chemical  Changes  during  Cooking;  General  Changes 
affecting  Cellulose,  Starch,  Sugar,  Pectin  Bodies,  Fats, 


V1U  CONTENTS 

PAGE 

Proteids ;  Effect  of  Chemical  Changes  on  Digestibility ; 
Physical  Changes  during  Cooking;  Action  of  Heat  on 
Animal  and  Plant  Tissues  ;  Amount  of  Heat,  required  for 
Cooking ;  Bacteriological  Changes  ;  Insoluble  Ferments  ; 
Soluble  Ferments ;  Bacterial  Action  Necessary  in  Prepa- 
ration of  Some  Foods  ;  Injurious  Bacterial  Action ;  Gen- 
eral Relationship  of  Chemical,  Physical,  and  Bacteriological 
Changes ;  Esthetic  Value  of  Foods ;  Color  of  Foods, 
Natural  and  Artificial  Colors ;  Conditions  under  which 
Use  of  Chemicals  in  Preparation  of  Foods  is  Justifiable. 


CHAPTER   III 

VEGETABLE  FOODS        . 

General  Composition;  Potatoes;  Chemical  and  Me- 
chanical Composition ;  Uses  of  Potatoes  in  Dietary ;  Sweet 
Potatoes ;  Carrots ;  Parsnips,  Cabbage ;  Cauliflower ; 
Beets  ;  Cucumbers  ;  Lettuce ;  Onions  ;  Spinach  ;  Aspara- 
gus ;  Melons ;  Tomatoes ;  Sweet  Corn ;  Eggplant ; 
Squash  ;  Celery  ;  Dietetic  Value  of  Vegetables  ;  Nutrient 
Content  of  Vegetables  ;  Sanitary  Condition  of  Vegetables  ; 
Miscellaneous  Compounds  in  Vegetables ;  Canned  Vege- 
tables ;  Edible  Portion  and  Refuse  of  Vegetables. 

CHAPTER   IV 

FRUITS,  FLAVORS,  AND  EXTRACTS 

General  Composition ;  Food  Value ;  Apples  ;  Oranges ; 
Lemons  ;  Grape  Fruit ;  Strawberries ;  Grapes  ;  Peaches  ; 
Plums ;  Olives ;  Figs ;  Dried  Fruits ;  Uses  of  Fruit  in 
the  Dietary ;  Canning  and  Preservation  of  Fruits ;  Adul- 
terated Canned  Fruits  ;  Fruit  Flavors  and  Extracts  ;  Syn- 
thetic Preparation  of  Flavors. 


CONTENTS  ix 

CHAPTER   V 

PAGE 

SUGARS,  MOLASSES,  SYRUP,  HONEY,  AND  CONFECTIONS      .      58 

Composition  of  Sugars ;  Beet  Sugar ;  Cane  Sugar ; 
Manufacture  of  Sugar ;  Sulphur  Dioxid  and  Indigo,  Uses 
of,  in  Sugar  Manufacture ;  Commercial  Grades  of  Sugar ; 
Sugar  in  the  Dietary ;  Maple  Sugar ;  Adulteration  of 
Sugar ;  Dextrose  Sugars  ;  Inversion  of  Sugars  ;  Molasses  ; 
Syrups ;  Adulteration  of  Molasses ;  Sorghum  Syrup ; 
Maple  Syrup  ;  Analysis  of  Sugar ;  Adulteration  of  Syrups  ; 
Honey ;  Confections  ;  Coloring  Matter  in  Candies ;  Coal 
Tar  Dyes ;  Saccharine. 

CHAPTER  VI 

LEGUMES  AND  NUTS 71 

General  Composition  of  Legumes;  Beans;  Digesti- 
bility of  Beans ;  Use  of  Beans  in  the  Dietary ;  String 
Beans  ;  Peas  ;  Canned  Peas  ;  Peanuts  ;  General  Compo- 
sition of  Nuts  ;  Chestnuts  ;  The  Hickory  Nut ;  Almonds  ; 
Pistachio  ;  Cocoanuts  ;  Uses  of  Nuts  in  the  Dietary. 

CHAPTER   VII 

MILK  AND  DAIRY  PRODUCTS 80 

Importance  in  the  Dietary ;  General  Composition ;  Di- 
gestibility ;  Sanitary  Condition  of  Milk ;  Certified  Milk ; 
Pasteurized  Milk ;  Tyrotoxicon ;  Color  of  Milk ;  Souring 
of  Milk  ;  Use  of  Preservatives  in  Milk  ;  Condensed  Milk  ; 
Skim  Milk  ;  Cream  ;  Buttermilk  ;  Goat's  Milk ;  Koumiss  ; 
Prepared  Milks ;  Human  Milk ;  Adulteration  of  Milk ; 
Composition  of  Butter;  Digestibility  of  Butter;  Adul- 
teration of  Butter;  General  Composition  of  Cheese; 
Digestibility ;  Use  in  the  Dietary ;  Cottage  Cheese  ;  Differ- 


CONTENTS 


ent  Kinds   of  Cheese ;    Adulteration   of  Cheese ;    Dairy 
Products  in  the  Dietary. 


CHAPTER   VIII 

MEATS  AND  ANIMAL  FOOD  PRODUCTS 

General  Composition ;  Mineral  Matter ;  Fat ;  Protein ; 
Non-nitrogenous  Compounds ;  Why  Meats  vary  in  Com- 
position ;  Amides ;  Albuminoids ;  Taste  and  Flavor  of 
Meats ;  Alkaloidal  Bodies  in  Meats ;  Ripening  of  Meats 
in  Cold  Storage  ;  Beef ;  Veal ;  Mutton  ;  Pork  ;  Lard  ; 
Texture  and  Toughness  of  Meat ;  Influence  of  Cooking 
upon  the  Composition  of  Meats  ;  Beef  Extracts  ;  Miscel- 
laneous Meat  Products ;  Pickled  Meats ;  Saltpeter  in 
Meats  ;  Smoked  Meats  ;  Poultry ;  Fish  ;  Oysters,  Fatten- 
ing of ;  Shell  Fish  ;  Eggs,  General  Composition  ;  Digesti- 
bility of  Eggs;  Use  of  Eggs  in  the  Dietary;  Canned 
Meats,  General  Composition. 


CHAPTER   IX 

CEREALS        ....        

Preparation  and  Cost  of  Cereals ;  Various  Grains  used 
in  making  Cereal  Products;  Cleanliness  of;  Corn  Prepa- 
rations ;  Corn  Flour ;  Use  of  Corn  in  Dietary  ;  Corn  Bread  ; 
Oat  Preparations  ;  Cooking  of  Oatmeal ;  Wheat  Prepara- 
tions ;  Flour  Middlings;  Breakfast  Foods;  Digestibility 
of  Wheat  Preparations  ;  Barley  Preparations  ;  Rice  Prepa- 
rations ;  Predigested  Foods  ;  The  Value  of  Cereals  in  the 
Dietary ;  Phosphate  Content  of  Cereals  ;  Phosphorus  Re- 
quirements of  a  Ration ;  Mechanical  Action  of  Cereals 
upon  Digestion  ;  Cost  and  Nutritive  Value  of  Cereals. 


CONTENTS  Xi 

CHAPTER  X 

PAGE 

WHEAT  FLOUR 133 

Use  for  Bread  Making ;  Winter  and  Spring  Wheat 
Flours  ;  Composition  of  Wheat  and  Flour ;  Roller  Process 
of  Flour  Milling  ;  Grad es  of  Flour ;  Types  of  Flour ;  Com- 
position of  Flour;  Graham  and  Entire  Wheat  Flours; 
Composition  of  Wheat  Offals  ;  Aging  and  Curing  of  Flour ; 
Macaroni  Flour ;  Color ;  Granulation ;  Capacity  of  Flour 
to  absorb  Water ;  Physical  Properties  of  Gluten ;  Gluten 
as  a  Factor  in  Bread  Making ;  Unsoundness  ;  Comparative 
Baking  Tests ;  Bleaching ;  Adulteration  of  Flour ;  Nutri- 
tive Value  of  Flour. 


CHAPTER  XI 

BREAD  AND  BREAD  MAKING 158 

Leavened  and  Unleavened  Bread ;  Changes  during 
Bread  Making  ;  Loss  of  Dry  Matter  during  Bread  Making ; 
Action  of  Yeast ;  Compressed  Yeast ;  Dry  Yeast ;  Pro- 
duction of  Carbon  Dioxid  Gas  and  Alcohol ;  Production 
of  Soluble  Carbohydrates ;  Production  of  Acids  in  Bread 
Making;  Volatile  Compounds  produced  during  Bread 
Making ;  Behavior  of  Wheat  Proteids  in  Bread  Making ; 
Production  of  Volatile  Nitrogenous  Compounds ;  Oxida- 
tion of  Fat ;  Influence  of  the  Addition  of  Wheat  Starch 
and  Gluten  to  Flour;  Composition  of  Bread;  Use  of 
Skim  Milk  and  Lard  in  Bread  Making;  Influence  of 
Warm  and  Cold  Flours  in  Bread  Making ;  Variations  in 
the  Process  of  Bread  Making ;  Digestibility  of  Bread ; 
Use  of  Graham  and  Entire  Wheat  in  the  Dietary ;  Min- 
eral Content  of  White  Bread ;  Comparative  Digestibility 
of  New  and  Old  Bread ;  Different  Kinds  of  Bread  ;  Toast. 


Xll  CONTENTS 

CHAPTER  XII 

BAKING  POWDERS 

General  Composition ;  Cream  of  Tartar  Powders ;  Resi- 
due from  Cream  of  Tartar  Baking  Powders;  Tartaric 
Acid  Powders ;  Phosphate  Baking  Powders ;  Mineral  and 
Organic  Phosphates ;  Phosphate  Residue ;  Alum  Baking 
Powders ;  Residue  from  Alum  Baking  Powders ;  Objec- 
tions urged  against  Alum  Powders ;  Action  of  Baking 
Powders  and  Yeast  Compared ;  Keeping  Qualities  of 
Baking  Powders ;  Inspection  of  Baking  Powders  ;  Fillers  ; 
Home-made  Baking  Powders. 

CHAPTER  XIII 

VINEGAR,  SPICES,  AND  CONDIMENTS 

Vinegar;  Chemical  Changes  during  Manufacture  of 
Vinegar ;  Ferment  Action  ;  Materials  used  in  Preparation 
of  Vinegars  ;  Characteristics  of  a  Good  Vinegar ;  Vinegar 
Solids  ;  Acidity  of  Vinegar ;  Different  Kinds  of  Vinegars  ; 
Standards  of  Purity  ;  Adulteration  of  Vinegar ;  Character- 
istics of  Spices  ;  Pepper  ;  Cayenne  ;  Mustard  ;  Ginger ; 
Cinnamon  and  Cassia ;  Cloves  ;  Allspice  ;  Nutmeg ;  Adul- 
teration of  Spices  and  Condiments ;  Essential  Oils  of; 
Uses  of  Condiments  in  Preparation  of  Foods ;  Action  of 
Condiments  upon  Digestion ;  Condiments  and  Natural 
Flavors. 

CHAPTER  XIV 
TEA,  COFFEE,  CHOCOLATE,  AND  COCOA       .... 

Tea ;  Sources  of  Tea  Supply ;  Composition  of  Tea ; 
Black  Tea  and  Green  Tea ;  Judging  Teas ;  Adulteration 
of  Tea ;  Food  Value  and  Physiological  Properties  of  Tea ; 


CONTENTS  Xlii 

PAGE 

Composition  of  Coffee  ;  Adulteration  of  Coffee ;  Chicory 
in  Coffee  ;  Glazing  of  Coffee  ;  Cereal  Coffee  Substitutes ; 
Cocoa  and  Chocolate  Preparations  ;  Composition  of  Cocoa ; 
Chocolate  ;  Cocoa  Nibs  ;  Plain  Chocolate ;  Sweet  Choco- 
late ;  Cocoa  Butter ;  Nutritive  Value  of  Cocoa ;  Adultera- 
tion of  Chocolate  and  Cocoa;  Comparative  Composition 
of  Beverages. 

CHAPTER  XV 

THE  DIGESTIBILITY  OF  FOODS 214 

Digestibility,  how  Determined ;  Completeness  and  Ease 
of  Digestion  Process  ;  Example  of  Digestion  Experiment ; 
Available  Nutrients  ;  Available  Energy  ;  Caloric  Value  of 
Foods ;  Normal  Digestion  and  Health ;  Digestibility  of 
Animal  Foods  ;  Digestibility  of  Vegetable  Foods ;  Factors 
influencing  Digestion ;  Combination  of  Foods ;  Amount 
of  Food ;  Method  of  Preparation  of  Food ;  Mechanical 
Condition  of  Foods  ;  Mastication  ;  Palatability  of  Foods ; 
Physiological  Properties  of  Foods;  Individuality;  Psy- 
chological Factors. 

CHAPTER  XVI 
COMPARATIVE  COST  AND  VALUE  OF  FOODS         .        .        .231 

Cost  and  Nutrient  Content  of  Foods ;  How  to  compare 
Two  Foods  as  to  Nutritive  Value  ;  Cheap  Foods  ;  Expen- 
sive Foods ;  Nutrients  Procurable  for  a  Given  Sum ;  Ex- 
amples ;  Comparing  Nutritive  Value  of  Common  Foods 
at  Different  Prices  ;  Cost  and  Value  of  Nutrients. 

CHAPTER  XVII 
DIETARY  STUDIES 244 

Object  of  Dietary  Studies  ;  Wide  and  Narrow  Rations; 
Dietary  Standards ;  Number  of  Meals  per  Day ;  Mixed 


XIV  CONTENTS 

PAGE 

Dietary  Desirable ;  Animal  and  Vegetable  Foods ; 
Economy  of  Production  ;  Food  Habits ;  Underfed  Fami- 
lies ;  Cheap  and  Expensive  Foods ;  Food  Notions ; 
Dietary  of  Two  Families  Compared ;  Food  in  its  Relation 
to  Mental  and  Physical  Vigor;  Dietary  Studies  in  Public 
Institutions. 

CHAPTER  XVIII 

RATIONAL  FEEDING  OF  MAN 261 

Object ;  Human  and  Animal  Feeding  Compared  ;  Stand- 
ard Rations  ;  Why  Tentative  Dietary  Standards  ;  Amounts 
of  Food  Consumed ;  Average  Composition  of  Foods ; 
Variations  in  Composition  of  Foods ;  Example  of  a  Ra- 
tion ;  Calculations  of  Balanced  Rations ;  Requisites  of  a 
Balanced  Ration  ;  Examples  ;  Calculations  of  Rations  for 
Men  at  Different  Kinds  of  Labor. 

CHAPTER  XIX 
WATER 268 

Importance;  Impurities  in  Water;  Mineral  Impurities; 
Organic  Impurities  ;  Interpretation  of  a  Water  Analysis  ; 
Natural  Purification  of  Water;  Water  in  Relation  to 
Health  ;  Improvement  of  Waters  ;  Boiling  of  Water ;  Fil- 
tration ;  Purification  of  Water  by  Addition  of  Chemicals  ; 
Ice;  Rain  Waters;  Waters  of  High  and  Low  Purity; 
Chemical  Changes  which  Organic  Matter  of  Water  Un- 
dergoes;  Bacterial  Content  of  Water;  Mineral  Waters; 
Materials  for  Softening  Water ;  Uses  of ;  Economic  Value 
of  a  Pure  Water  Supply. 

CHAPTER   XX 

FOOD    AS    AFFECTED    BY    HOUSEHOLD    SANITATION    AND 

STORAGE 284 

Injurious  Compounds  in  Foods ;  Nutrient  Content  and 


CONTENTS  XV 

PAGE 

Sanitary  Condition  of  Food ;  Sources  of  Contamination 
of  Food ;  Unclean  Ways  of  Handling  Food  ;  Sanitary  In- 
spection of  Food ;  Infection  from  Impure  Air ;  Storage 
of  Food  in  Cellars ;  Respiration  of  Vegetable  Cells  ;  Sun- 
light, Pure  Water,  and  Pure  Air  as  Disinfectants ;  Foods 
contaminated  from  Leaky  Plumbing  ;  Utensils  for  Storage 
of  Food ;  Contamination  from  Unclean  Dishcloths ;  Re- 
frigeration ;  Chemical  Changes  that  take  Place  in  the 
Refrigerator;  Soil;  Disposal  of  Kitchen  Refuse;  Germ 
Diseases  spread  by  Unsanitary  Conditions  around  Dwell- 
ings due  to  Contamination  of  Food ;  General  Considera- 
tions ;  Relation  of  Food  to  Health. 

CHAPTER  XXI 

LABORATORY  PRACTICE 299 

Object  of  Laboratory  Practice ;  Laboratory  Note-book 
and  Suggestions  for  Laboratory  Practice ;  List  of  Appara- 
tus Used;  Photograph  of  Apparatus  Used;  Directions 
for  Weighing ;  Directions  for  Measuring ;  Use  of  Micro- 
scope ;  Water  in  Flour ;  Water  in  Butter ;  Ash  in  Flour ; 
Nitric  Acid  Test  for  Nitrogenous  Organic  Matter ;  Acidity 
of  Lemons ;  Influence  of  Heat  on  Potato  Starch  Grains ; 
Influence  of  Yeast  on  Starch  Grains  ;  Mechanical  Compo- 
sition of  Potatoes  ;  Pectose  from  Apples  ;  Lemon  Extract ; 
Vanilla  Extract ;  Testing  Olive  Oil  for  Cotton  Seed  Oil ; 
Testing  for  Coal  Tar  Dyes  ;  Determining  the  Per  Cent  of 
Skin  in  Beans ;  Extraction  of  Fat  from  Peanuts ;  Micro- 
scopic Examination  of  Milk ;  Formaldehyde  in  Cream  or 
Milk  ;  Gelatine  in  Cream  or  Milk  ;  Testing  for  Oleomarga- 
rine ;  Testing  for  Watering  or  Skimming  of  Milk ;  Boric 
Acid  in  Meat ;  Microscopic  Examination  of  Cereal  Starch 
Grains;  Identification  of  Commercial  Cereals;  Granula- 
tion and  Color  of  Flour;  Capacity  of  Flour  to  absorb 


XVI  CONTENTS 

PAGE 

Water ;  Acidity  of  Flour ;  Moist  and  Dry  Gluten ;  Gliadin 
from  Flour;  Bread-making  Test ; .Microscopic  Examina- 
tion of  Yeast ;  Testing  Baking  Powders  for  Alum ;  Test- 
ing Baking  Powders  for  Phosphoric  Acid  ;  Testing  Baking 
Powders  for  Ammonia ;  Vinegar  Solids  ;  Specific  Gravity 
of  Vinegar ;  Acidity  of  Vinegar ;  Deportment  of  Vinegar 
with  Reagents  ;  Testing  Mustard  for  Turmeric ;  Examina- 
tion of  Tea  Leaves ;  Action  of  Iron  Compounds  upon 
Tannic  Acid ;  Identification  of  Coffee  Berries  ;  Detecting 
Chicory  in  Coffee ;  Comparative  Amounts  of  Soap  Neces- 
sary with  Hard  and  Soft  Water ;  Solvent  Action  of  Water 
on  Lead;  Suspended  Matter  in  Water;  Organic  Matter 
in  Water ;  Deposition  of  Lime  by  Boiling  Water ;  Quali- 
tative Tests  for  Minerals  in  Water;  Testing  for  Nitrites 
in  Water. 

REVIEW  QUESTIONS .        .    323 

REFERENCES 350 

INDEX 357 


HUMAN    FOODS    AND    THEIR 
NUTRITIVE   VALUE 


HUMAN  FOODS  AND  THEIR 
NUTRITIVE  VALUE 

CHAPTER   I 
GENERAL   COMPOSITION   OF   FOODS 

1.  Water.  —  All  foods  contain  water.  Vegetables  in 
their  natural  condition  contain  large  amounts,  often  95 
per  cent,  while  in  meats  there  is  from  40  to  60  per  cent 
or  more.  Prepared  cereal  products,  as  flour,  corn  meal, 
and  oatmeal,  which  are  apparently  dry,  have  from  7  to 
14  per  cent.  In  general  the  amount  of  water  in  a  food 
varies  with  the  mechanical  structure  and  the  conditions 
under  which  it  has  been  prepared,  and  is  an  important 
factor  in  estimating  the  value,  as  the  nutrients  are  often 
greatly  decreased  because  of  large  amounts  of  water. 
The  water  in  substances  as  flour  and  meal  is  mechani- 
cally held  in  combination  with  the  fine  particles  and 
varies  with  the  moisture  content,  or  hydroscopicity,  of 
the  air.  Oftentimes  foods  gain  or  lose  water  to  such 
an  extent  as  to  affect  their  weight;  for. example,  one 
hundred  pounds  of  flour  containing  12  per  cent  of 
water  may  be  reduced  in  weight  three  pounds  or  more 
when  stored  in  a  dry  place,  or  there  may  be  an  increase 

B  I 


2  HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

in  weight  from  being  stored  in  a  damp  place.  In 
tables  of  analyses  the  results,  unless  otherwise  stated, 
are  usually  given  on  the  basis  of1  the  original  material, 
or  the  dry  substance.  Potatoes,  for  example,  contain 
2\  per  cent  of  crude  protein  on  the  basis  of  75  per  cent 
of  water;  or  on  a  dry  matter  basis,  that  is,  when  the 
water  is  entirely  eliminated,  there  is  10  per  cent  of 
protein. 

The  water  of  foods  is  determined  by  drying  the 
weighed  material  in  a  water  or  air  oven  at  a  tempera- 
ture of  about  100°  C,  until  all  of  the  moisture  has  been 
expelled  in  the  form  of  steam,  leaving  the  dry  matter  or 
material  free  from  water.1  The  determination  of  dry 
matter,  while  theoretically  a  simple  process,  is  attended 
with  many  difficulties.  Substances  which  contain  much 
fat  may  undergo  oxidation  during  drying;  volatile  com- 
pounds, as  essential  oils,  are  expelled  along  with  the 
moisture;  and  other  changes  may  occur  affecting  the 
accuracy  of  the  work.  The  last  traces  of  moisture  are 
removed  with  difficulty  from  a  substance,  being  me- 
chanically retained  by  the  particles  with  great  tenacity. 
When  very  accurate  dry  matter  determinations  are  de- 
sired, the  substance  is  dried  in  a  vacuum  oven,  or  in  a 
desiccator  over  sulphuric  acid,  or  in  an  atmosphere  of 
some  non-oxidizing  gas,  as  hydrogen. 

2.  Dry  Matter.  —  The  dry  matter  of  a  food  is  a  me- 
chanical mixture  of  the  various  compounds,  as  starch, 
sugar,  fat,  protein,  cellulose,  and  mineral  matter,  and  is 


GENERAL  COMPOSITION  OF  FOODS 


FIG.  i.  — APPARATUS  USED  FOR  THE  DETERMINATION  OF  DRY  MATTER 
AND  ASH  IN  FOODS. 

i,  desiccator;  2,  muffle  furnace  for  combustion  of  foods  and  obtaining  ash; 
3,  water  oven  for  drying  food  materials. 

obtained  by  drying  the  material.     Succulent  vegetable 
foods  with  95  per  cent  of  water  contain  only  5  per  cent 


4  HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

of  dry  matter,  while  in  flour  with  12  per  cent  of  water 
there  is  88  per  cent,  and  in  sugar  99  per  cent.  The 
dry  matter  is  obtained  by  subtracting  ,  the  per  cent  of 
water  from  100,  and  in  foods  it  varies  from  5  per  cent 
and  less  in  some  vegetables  to  99  per  cent  in  sugar. 

3.  Ash.  —  The  ash,  or  mineral  matter,  is  that  portion 
obtained  by  burning  or  igniting  the  dry  matter  at  the 
lowest  temperature  necessary  for  complete  combustion. 
The  ash  in  vegetable  foods  ranges  from  2  to  5  per  cent 
and,  together  with  the  nitrogen,  represents  what  was 
taken  from  the  soil  during  growth.  In  animal  bodies, 
the  ash  is  present  mainly  in  the  bones,  but  there  is  also 
an  appreciable  amount,  one  per  cent  or  more,  in  all  the 
tissues.  Ash  is  exceedingly  variable  in  composition, 
being  composed  of  the  various  salts  of  potassium,  so- 
dium, calcium,  magnesium,  and  iron,  as  sulphates,  phos- 
phates, chlorides,  and  silicates  of  these  elements.  There 
are  also  other  elements  in  small  amounts.  In  the  plant 
economy  these  elements  take  an  essential  part  and  are 
requisite  for  the  formation  of  plant  tissue  and  the  pro- 
duction in  the  leaves  of  the  organic  compounds  which 
later  are  stored  up  in  the  seeds.  Some  of  the  elements 
appear  to  be  more  necessary  than  others,  and  whenever 
withheld  plant  growth  is  restricted.  The  elements 
most  essential  for  plant  growth  are"  potassium,  calcium, 
magnesium,  iron,  phosphorus,  and  sulphur.1 

In  the  animal  body  minerals  are  derived,  either  di- 
rectly or  indirectly,  from  the  vegetable  foods  consumed. 


GENERAL  COMPOSITION  OF  FOODS  5 

The  part  which  each  of  the  mineral  elements  takes  in 
animal  nutrition  is  not  well  understood.  Some  of  the 
elements,  as  phosphorus  and  sulphur,  are  in  organic 
combination  with  the  nitrogenous  compounds,  as  the 
nucleated  albuminoids,  which  are  very  essential  for  ani- 
mal life.  In  both  plant  and  animal  bodies,  the  mineral 
matter  is  present  as  mineral  salts  and  organic  combina- 
tions. It  is  held  that  the  ash  elements  which  are  in 
organic  combination  are  the  forms  mainly  utilized  for 
tissue  construction.  While  it  is  not  known  just  what 
part  all  the  mineral  elements  take  in  animal  nutrition, 
experiments  show  that  in  all  ordinary  mixed  rations  the 
amount  of  the  different  mineral  elements  is  in  excess 
of  the  demands  of  the  body,  and  it  is  only  in  rare 
instances,  as  in  cases  of  restricted  diet,  or  convalescence 
from  some  disease,  that  special  attention  need  be  given 
to  increasing  the  mineral  content  of  the  ration.  An  ex- 
cess of  mineral  matter  in  foods  is*  equally  as  objection- 
able as  a  scant  amount,  elimination  of  the  excess  entail- 
ing additional  work  on  the  body. 

The  composition  of  the  ash  of  different  food  mate- 
rials varies  widely,  both  in  amount,  and  form  of  the 
individual  elements.  When  for  any  reason  it  is  neces- 
sary to  increase  the  phosphates  in  a  ration,  milk  and 
eggs  do  this  to  a  greater  extent  than  almost  any  other 
foods.  Common  salt,  or  sodium  chloride,  is  one  of  the 
most  essential  of  the  mineral  constituents  of  the  body. 
It  is  necessary  for  giving  the  blood  its  normal  composi- 
tion, furnishing  acid  and  basic  constituents  for  the  pro- 


6  HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

duction  of  the  digestive  fluids,  and  for  the  nutrition 
of  the  cells.  While  salt  is  a  necessary  food,  in  large 
amounts,  as  when  the  attempt  is  made  to  use  sea  water 
as  a  beverage,  it  acts  as  a  poison,  suggesting  that  a  ma- 
terial may  be  both  a  food  and  a  poison.  When  sodium 
chloride  is  entirely  withheld  from  an  animal,  death 
from  salt  starvation  ensues.  Many  foods  contain  natu- 
rally small  amounts  of  sodium  chloride. 

4.  Organic  Matter.  —  That  portion  of  a  food  material 
which  is  converted  into  gaseous  or  volatile  products 
during  combustion  is  called  the  organic  matter.  It  is 
a  mechanical  mixture  of  compounds  made  up  of  car- 
bon, hydrogen,  oxygen,  nitrogen,  and  sulphur,  and  is 
composed  of  various  individual  organic  compounds,  as 
cellulose,  starch,  sugar,  albumin,  and  fat.  The  amount 
in  a  food  is  determined  by  subtracting  the  ash  and 
water  from  100.  The  organic  matter  varies  widely  in 
composition ;  in  some  foods  it  is  largely  starch,  as  in 
potatoes  and  rice,  while  in  others,  as  forage  crops  con- 
sumed by  animals,  cellulose  predominates.  The  na- 
ture of  the  prevailing  organic  compound,  as  sugar  or 
starch,  determines  the  nutritive  value  of  a  food.  Each 
has  a  definite  chemical  composition  capable  of  being 
expressed  by  a  formula.  Considered  collectively,  the 
organic  compounds  are  termed  organic  matter.  When 
burned,  the  organic  compounds  are  converted  into 
gases,  the  carbon  uniting  with  the  oxygen  of  the  air 
to  form  carbon  dioxide,  hydrogen  to  form  water,  sul- 


GENERAL  COMPOSITION  OF  FOODS  7 

phur  to  form  sulphur  dioxide,  and  the  nitrogen  to  form 
oxides  of  nitrogen  and  ammonia. 

5.  Classification   of  Organic  Compounds.  —  All   food 
materials  are  composed  of  a  large  number  of  organic 
compounds.     For  purposes  of  study  these  are  divided 
into  classes.     The   element   nitrogen   is   taken   as   the 
basis  of   the  division.     Compounds  which  contain  this 
element  are  called  nitrogenous,  while  those  from  which 
it  is  absent  are  called  non-nitrogenous.2     The  nitroge- 
nous organic  compounds  are  composed  of  the  elements 
nitrogen,  hydrogen,  carbon,  oxygen,  and  sulphur,  while 
the  non-nitrogenous  compounds  are  composed  of  carbon, 
hydrogen,  and  oxygen.     In   vegetable  foods  the   non- 
nitrogenous  compounds  predominate,  there  being  usually 
from  six  to  twelve  parts  of  non-nitrogenous  to  every  one 
part  of  nitrogenous,  while  in  animal  foods  the  nitroge- 
nous compounds  are  present  in  larger  amount. 

NON-NITROGENOUS  COMPOUNDS 

6.  Occurrence.  —  The  non-nitrogenous  compounds  of 
foods  consist  mainly  of  cellulose,  starch,  sugar,  and  fat. 
For  purposes  of  study,  they  are  divided  into   subdivi- 
sions, as   carbohydrates,  pectose  substances   or  jellies, 
fats,  organic  acids,  essential  oils,  and  mixed  compounds. 
In  plants  the  carbohydrates  predominate,  while  in  ani- 
mal tissue  the  fats  are  the  chief  non-nitrogenous  con- 
stituents. 


8  HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

7.  Carbohydrates.  —  This  term  is  applied  to  a  class 
of  compounds  similar  in  general  composition,  but  dif- 
fering widely  in    structural   composition    and    physical 
properties.     Carbohydrates  make  up  the  bulk  of  vege- 
table foods  and,  except  in  milk,  are  found  only  in  traces 
in   animal   foods.      They    are    all   represented   by   the 
general   formula    CH2nOw,  there  being  twice   as  many 
hydrogen  as  oxygen  atoms,  the  hydrogen  and  oxygen 
being  present  in  the  same  proportion  as  in  water.     As 
a  class,  the  carbohydrates  are  neutral  bodies,  and,  when 
burned,  form  carbon  dioxide  and  water. 

8.  Cellulose  is  the  basis  of  the  cell  structure  of  plants, 
and  is  found  in   various    physical  forms   in   food   ma- 
terials.3     Sometimes   it   is    hard    and   dense,    resisting 
digestive  action  and  mechanically  inclosing  other  nutri- 
ents and  thus  preventing  their  being 
available    as    food.      In    the    earlier 
stages  of  plant  growth  a  part  of  the 
cellulose  is  in  chemical  combination 
with  water,  forming  hydrated  cellu- 
lose, a   portion  of   which  undergoes 
digestion  and  produces  heat  and  en- 
ergy in  the  body.     Ordinarily,  how- 

FIG.  2. —CELLULAR  ever,  cellulose  adds  but  little  in  the 
STRUCTURE  OF  way  of  nutritive  value,  although  it  is 
PLANT  CELL.  r  i  c.  -  i  u  •'  'n  j  • 

often  beneficial  mechanically  and  im- 
parts bulk  to  some  foods  otherwise  too  concentrated. 
The  mechanical  action  of  cellulose  on  the  digestion  of 


GENERAL  COMPOSITION  OF  FOODS          9 

food  is  discussed  in  Chapter  XV.  Cellulose  usually 
makes  up  a  very  small  part  of  human  food,  less  than  I 
per  cent.  In  refined  white  flour  there  is  less  than.  .05 
of  a  per  cent;  in  oatmeal  and  cereal  products  from  .5 
to  i  per  cent,  depending  upon  the  extent  to  which  the « 
hulls  are  removed,  and  in  vegetable  foods  from  .1  to  I 
per  cent.  The  cellulose  content  of  foods  is  included  in 
the  crude  fiber  of  the  chemist's  report. 

9.  Starch  occurs  widely  distributed  in  nature,  par- 
ticularly in  the  seeds,  roots,  and  tubers  of  some  plants. 
It  is  formed  in  the  leaves  of  plants  as  a  result  of  the 
joint  action  of  chlorophyll  and  protoplasm,  and  is  gen- 
erally held  by  plant  physiologists  to  be  the  first  carbohy- 
drate produced  in  the  plant  cell.  Starch  is  composed 
of  a  number  of  overlapping  layers  separated  by  starch 
cellulose ;  between  these  layers  the  true  starch  or  amy- 
lose  is  found.  Starch  from  the  various  cereals  and 
vegetables  differs  widely  in  mechanical  structure;  in 
wheat  it  is  circular,  in  corn  somewhat  angular,  and  in 
parsnips  exceedingly  small,  while  potato  starch  granules 
are  among  the  largest.4  The  nature  of  starch  can  be 
determined  largely  from  its  mechanical  structure  as 
studied  under  the  microscope.  It  is  insoluble  in  cold 
water  because  of  the  protecting  action  of  the  cellular 
layer,  but  on  being  heated  it  undergoes  both  mechanical 
and  chemical  changes ;  the  grains  are  partially  ruptured 
by  pressure  due  to  the  conversion  into  steam  of  the 
moisture  held  mechanically.  The  cooking  of  foods  is 


10        HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

4 

beneficial  from  a  mechanical  point  of  view,  as  it  results 
in  partial  disintegration  of  the  starch  masses,  changing 
the  structure  so  that  the  starch  is  more  readily  acted 
upon  by  the  ferments  of  the  digestive  tract.  At  a 
temperature  of  about  120°  C.  starch  begins  to  undergo 
chemical  change,  resulting  in  the  rearrangement  of  the 
atoms  in  the  molecule  with  the  production  of  dextrine 
and  soluble  carbohydrates.  Dextrine  is  formed  on  the 
crust  of  bread,  or  whenever  potatoes  or  starchy  foods 
are  browned.  At  a  still  higher  temperature  starch  is 
decomposed,  with  the  liberation  of  water  and  production 
of  compounds  of  higher  carbon  content.  When  heated  in 
contact  with  water,  it  undergoes  hy dration  changes ;  gelati- 
nous-like  products  are  formed,  which  are  finally  converted 
into  a  soluble  condition.  In  cooking  cereals,  the  hydra- 
tion  of  the  starch  is  one  of  the  main  physical  and 
chemical  changes  that  takes  place,  and  it  simply  results 
in  converting  the  material  into  such  a  form  that  other 
chemical  changes  may  more  readily  occur.  Before 
starch  becomes  dextrose,  hydration  is  necessary.  If 
this  is  accomplished  by  cooking,  it  saves  the  body  just 
so  much  energy  in  digestion.  Many  foods  owe  their 
value  largely  to  the  starch.  In  cereals  it  is  found  to 
the  extent  of  72  to  76  per  cent ;  in  rice  and  potatoes  in 
still  larger  amounts ;  and  it  is  the  chief  constituent  of 
many  vegetables.  When  starch  is  digested,  it  is  first: 
changed  to  a  soluble  form  and  then  gradually  undergoes 
oxidation,  resulting  in  the  production  of  heat  and  energy, 
the  same  products  —  carbon  dioxide  and  water  —  being 


GENERAL  COMPOSITION  OF  FOODS          II 

formed  as  when  starch  is  burned.  Starch  is  a  valu- 
able heat-producing  nutrient;  a  pound  yields  1860 
calories.  See  Chapter  XV. 

10.  Sugar.  —  Sugars  are  widely  distributed  in  nature, 
being  found  principally  in  the  juices  of  the  sugar  cane, 
sugar  beet,  and  sugar  maple.     They  are  divided   into 
two  large  classes  :  the  sucrose  group  and  the  dextrose 
group,  the  latter  being  produced  from  sucrose,  starch, 
and  other  carbohydrates  by  inversion  and  allied  chemi- 
cal changes.     Because  of  the  importance   of   sugar  in 
the  dietary,  Chapter  V  is  devoted  to  the  subject. 

11.  Pectose  Substances  are  jelly-like  bodies  found  in 
fruits   and  vegetables.      They    are   closely   related    in 
chemical  composition  to  the  carbohydrates,  into  which 
form  they  are  changed  during  digestion ;  and  in  nutri- 
tion they  serve  practically  the  same  function.     In  the 
early  stages  of  growth  the  pectin  bodies  are  combined 
with  organic  acids,  forming  insoluble  compounds,  as  the 
pectin  in  green  apples.     During  the  ripening  of  fruit 
and  the  cooking  of  vegetables,  the  pectin  is  changed  to 
a  more  soluble  and  digestible  condition.     In  food  analy- 
sis, the  pectin  is  usually   included  with    the   carbohy- 
drates. 

12.  Nitrogen-free-extract.  —  In   discussing   the  com- 
position of  foods,   the  carbohydrates  other  then  cellu- 
lose, as  starch,  sugar,  and  pectin,  are  grouped  under 
the  name  of  nitrogen-free-extract.     Methods  of  chemi 


12          HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

cal  analysis  have  not  yet  been  sufficiently  perfected  to 
enable  accurate  and  rapid  determination  to  be  made  of 
all  these  individual  carbohydrates,  and  hence  they  are 
grouped  together  as  nitrogen-free-extract.  As  the 
name  indicates,  they  are  compounds  which  contain  no 
nitrogen,  and  are  extractives  in  the  sense  that  they  are 
soluble  in  dilute  acid  and  alkaline  solutions.  The  nitro- 
gen-free-extract is  determined  indirectly,  that  is,  by  the 
method  of  difference.  All  the  other  constituents  of  a 
food,  as  water,  ash,  crude  fiber  (cellulose),  crude  protein, 
and  ether  extract,  are  determined ;  the  total  is  subtracted 
from  100,  and  the  difference  is  nitrogen-free-extract. 
In  studying  the  nutritive  value  of  foods,  particular 
attention  should  be  given  to  the  nature  of  the  nitrogen- 
free-extract,  as  in  some  instances  it  is  composed  of 
sugar  and  in  others  of  starch,  pectin,  or  pentosan  (gum 
sugars).  While  all  these  compounds  harve  practically 
the  same  fuel  value,  they  differ  in  composition,  struc- 
ture, and  the  way  in  which  they  are  acted  upon  by 
chemicals  and  digestive  ferments.1 

13.  Fat.  —  Fat  is  found  mainly  in  the  seeds  of  plants, 
but  to  some  extent  in  the  leaves  and  stems.  It  differs 
from  starch  in  containing  more  carbon  and  less  oxygen. 
In  starch  there  is  about  44  per  cent  of  carbon,  while  in 
fat  there  is  75  per  cent.  Hence  it  is  that  when  fat  is 
burned  or  undergoes  combustion,  it  yields  a  larger 
amount  of  the  products  of  combustion  —  carbon  dioxid 
and  water — than  does  starch.  A  gram  of  fat  produces 


GENERAL  COMPOSITION  OF  FOODS 


2\  times  as  much  heat  as  a  gram  of  starch.  Fat  is 
the  most  concentrated  non-nitrogenous  nutrient.  As 
found  in  food  mate- 
rials, it  is  a  mechani- 
cal mixture  of  various 
fats,  among  which  are 
stearin,  palmitin,  and 
olein.  Stearin  and 
palmitin  are  hard  fats, 
crystalline  in  struc- 
ture, and  with  a  high 
melting  point,  while 
olein  is  a  liquid.  In  ad- 
dition to  these  three, 
there  are  also  small 
amounts  of  other  fats, 
as  butyrin  in  butter, 
which  give  character 
or  individuality  to  ma- 
terials. There^afe^. 
number  of  vegetable 
fats  or  oils  which  are 
used  for  food  pur- 
poses and,  when  prop- 
erly prepared  and 
refined,  have  a  high 
nutritive  value.  Occa- 
sionally one  fat  of  cheaper  origin  but  not  necessarily  of 
lower  nutritive  value  is  substituted  for  another.  The 


FIG.  3.  — APPARATUS  USED  FOR  THE  DETER- 
MINATION OF  FAT. 


14        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

fats  have  definite  physical  and  chemical  properties  which 
enable  them  to  be  readily  distinguished,  as  iodine  num- 
ber, specific  gravity,  index  of  refraction,  and  heat  of  com- 
bustion. By  iodine  number  is  meant  the  percentage  of 
iodine  that  will  unite  chemically  with  the  fat.  Wheat  oil 
has  an  iodine  number  of  about  100,  meaning  that  one 
pound  of  wheat  oil  will  unite  chemically  with  one  pound 
of  iodine.  Fats  have  a  lower  specific  gravity  than  water, 
usually  ranging  from  .89  to  .94,  the  specific  gravity  of 
a  fat  being  fairly  constant.  All  fats  can  be  separated 
into  glycerol  and  a  fatty  acid,  glycerol  or  glycerine  being 
common  constituents,  while  each  fat  yields  its  own 
characteristic  acid,  as  stearin,  stearic  acid;  palmitin, 
palmitic  acid ;  and  olein,  oleic  acid.  The  fats  are 
soluble  in  ether,  chloroform,  and  benzine.  In  the 
chemical  analysis  of  foods,  they  are  separated  with 
ether,  and  along  with  the  fat,  variable  amounts  of  other 
substances  are  extracted,  these  extractive  products 
usually  being  called  "  ether  extract  "  or  "  crude  fat."  5 
The  ether  extract  of  plant  tissue  contains  in  addition  to 
fat  appreciable  amounts  of  cellulose,  gums,  coloring,  and 
other  materials.  From  cereal  products  the  ether  extract 
is  largely  fat,  but  in  some  instances  lecithin  and  other 
nitrogenous  fatty  substances  are  present,  while  in  animal 
food  products,  as  milk  and  meat,  the  ether  extract  is 
nearly  pure  fat. 

14.    Organic   Acids.  —  Many   vegetable  foods  contain 
small  amounts  of  organic  acids,  as  malic  acid  found  in 


GENERAL    COMPOSITION    OF    FOODS  15 

apples,  citric  in  lemons,  and  tartaric  in  grapes.  These 
give  characteristic  taste  to  foods,  but  have  no  direct 
nutritive  value.  They  do  not  yield  heat  and  energy  as 
do  starch,  fat,  and  protein ;  they  are,  however,  useful  for 
imparting  flavor  and  palatability,  and  it  is  believed  they 
promote  to  some  extent  the  digestion  of  foods  with 
which  they  are  combined  by  encouraging  the  secretion 
of  the  digestive  fluids.  Many  fruits  and  vegetables  owe 
their  dietetic  value  to  the  organic  acids  which  they  con- 
tain. In  plants  they  are  usually  in  chemical  combina- 
tion with  the  minerals,  forming  compounds  as  salts,  or 
with  the  organic  compounds,  producing  materials  as 
acid  proteins.  In  the  plant  economy  they  take  an 
essential  part  in  promoting  growth  and  aiding  the  plant 
to  secure  by  osmotic  action  its  mineral  food  from  the 
soil.  Organic  acids  are  found  to  some  extent  in  animal 
foods,  as  the  various  lactic  acids  of  meat  and  milk. 
They  are  also  formed  in  food  materials  as  the  result  of 
ferment  action.  When  seeds  germinate,  small  amounts 
of  carbohydrates  are  converted  into  organic  acids.  In 
general  the  organic  acids  are  not  to  be  considered  as 
nutrients,  but  as  food  adjuncts,  increasing  palatability 
and  promoting  digestion. 

15.  Essential  Oils.  —  Essential  or  volatile  oils  differ 
from  fats,  or  fixed  oils,  in  chemical  composition  and 
physical  properties.6  The  essential  oils  are  readily 
volatilized,  leaving  no  permanent  residue,  while  the 
fixed  fats  are  practically  non-volatile.  Various  essen- 


l6         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

tial  oils  are  present  in  small  amounts  in  nearly  all 
vegetable  food  materials,  and  tihe  characteristic  flavor 
of  many  fruits  is  due  to  them.  It  is  these  compounds 
which  are  used  for  flavoring  purposes,  as  discussed  in 
Chapter  IV.  The  amount  in  a  food  material  is  very 
small,  usually  only  a  few  hundredths  of  a  per  cent. 
The  essential  oils  have  no  direct  food  value,  but  in- 
directly, like  the  organic  acids,  they  assist  in  promoting 
favorable  digestive  action,  and  are  also  valuable  because 
they  impart  a  pleasant  taste.  Through  poor  methods  of 
cooking  and  preparation,  the  essential  oils  are  readily 
lost  from  some  foods. 

16.  Mixed  Compounds.  —  Food   materials  frequently 
contain  compounds  which  do  not  naturally  fall  into  the 
five   groups    mentioned,  —  carbohydrates,  pectose  sub- 
stances,   fats,    organic    acids,   and   essential  oils.     The 
amount  of  such  compounds  is  small,  and  they  are  classed 
as  miscellaneous  or  mixed  non-nitrogenous  compounds. 
Some  of  them  may  impart  a  negative  value  to  the  food, 
and  there  are  others  which  have  all  the  characteristics, 
as  far  as  general  composition  is  concerned,  of  the  non- 
nitrogenous  compounds,  but  contain  nitrogen,  although 
as  a  secondary  rather  than  an  essential  constituent. 

17.  Nutritive  Value  of  Non-nitrogenous  Compounds.  - 

The  non-nitrogenous  compounds,  taken  as  a  class,  are 
incapable  alone  of  sustaining  life,  because  they  do  not 
contain  any  nitrogen,  and  this  is  necessary  for  produc- 


GENERAL    COMPOSITION   OF    FOODS  17 

ing  proteid  material  in  the  animal  body.  They  are 
valuable  for  the  production  of  heat  and  energy,  and 
when  associated  with  the  nitrogenous  compounds,  are 
capable  of  forming  non-nitrogenous  reserve  tissue.  It 
is  equally  impossible  to  sustain  life  for  any  prolonged 
period  with  the  nitrogenous  compounds  alone.  It  is 
when  these  two  classes  are  properly  blended  and 
naturally  united  in  food  materials  that  their  main  value 
is  secured.  For  nutrition  purposes  they  are  mutually 
related  and  dependent.  Some  food  materials  contain 
the  nitrogenous  and  non-nitrogenous  compounds  blended 
in  such  proportion  as  to  enable  one  food  alone  to  prac- 
tically sustain  life,  while  in  other  cases  it  is  necessary, 
in  order  to  secure  the  best  results  in  the  feeding  of 
animals  and  men,  to  combine  different  foods  varying  in 
their  content  of  these  two  classes  of  compounds.7 

NITROGENOUS  COMPOUNDS 

18.  General  Composition. -- The  nitrogenous  com- 
pounds are  more  complex  in  composition  than  the  non- 
nitrogenous.  They  are  composed  of  a  larger  number 
of  elements,  united  in  different  ways  so  as  to  form  a 
much  more  complex  molecular  structure.  Foods  con- 
tain numerous  nitrogenous  organic  compounds,  which, 
for  purposes  of  study,  are  divided  into  four  divisions,— 
proteids,  albuminoids,  amids,  and  alkaloids.  In  addition 
to  these,  there  are  other  nitrogenous  compounds  which 
do  not  naturally  fall  into  any  one  of  the  four  divisions. 


1 8         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


FIG.  4.  — APPARATUS  USED  FOR  DETERMINING  TOTAL  NITROGEN  AND 
CRUDE  PROTEIN  IN  FOODS. 

The  material  is  digested  in  the  flask  (3)  with  sulphuric  acid  and  the  organic 
nitrogen  converted  into  ammonium  sulphate,  which  is  later  liberated  and 
distilled  at  i,  and  the  ammonia  neutralized  with  standard  acid  (2). 


GENERAL  COMPOSITION  OF  FOODS          19 

Also  in  some  foods  there  are  small  amounts  of  nitrogen 
in  mineral  forms,  as  nitrates  and  nitrites. 

19.  Protein.  —  The  term  "  protein  "  is  applied  to  a  large 
class  of  nitrogenous  compounds  resembling  each  other 
in  general  composition,  but  differing  widely  in  structural 
composition.  As  a  class,  the  proteins  contain  about  16 
per  cent  of  nitrogen,  52  per  cent  of  carbon,  from  6  to  7 
per  cent  of  hydrogen,  22  per  cent  of  oxygen,  and  less 
than  2  per  cent  of  sulphur.  These  elements  are  com- 
bined in  a  great  variety  of  ways,  forming  various  groups 
or  radicals.  In  studying  the  protein  molecule  a  large 
number  of  derivative  products  have  been  observed,  as 
amid  radicals,  various  hydrocarbons,  fatty  acids,  and 
carbohydrate-like  bodies.8  It  would  appear  that  in  the 
chemical  composition  of  the  proteins  there  are  all  the 
constituents,  or  simpler  products,  of  the  non-nitrogenous 
compounds,  and  these  are  in  chemical  combination  with 
amid  radicals  and  nitrogen  in  various  forms.  The  nitro- 
gen of  many  proteids  appears  to  be  present  in  more 
than  one  form  or  radical.  The  proteids  take  an  im- 
portant part  in  life  processes.  They  are  found  more 
extensively  in  animal  than  in  plant  bodies.  The  pro- 
toplasm of  both  the  plant  and  animal  cell  is  composed 
mainly  of  protein. 

Proteids  are  divided  into  various  subdivisions,  as 
albumins,  globulins,  albuminates,  proteoses  and  pep- 
tones, and  insoluble  proteids.  In  plant  and  animal 
foods  a  large  amount  of  the  protein  is  present  as  in- 


20        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

soluble  proteids ;  that  is,  they  are  not  dissolved  by  sol- 
vents, as  water  and  dilute  salt  solution.  The  albumins 
are  soluble  in  water  and  coagulated  by  heat  at  a  tem- 
perature of  157°  to  161°  F.  Whenever  a  food  material 
is  soaked  in  water,  the  albumin  is  removed  and  can 
then  be  coagulated  by  the  action  of  heat,  or  of  chemi- 
cals, as  tannic  acid,  lead  acetate,  and  salts  of  mercury. 
The  globulins  are  proteids  extracted  from  food  materials 
by  dilute  salt  solution  after  the  removal  of  the  albumins. 
Globulins  also  are  coagulated  by  heat  and  precipitated  by 
chemicals.  The  amount  of  globulins  in  vegetable  foods 
is  small.  In  animal  foods  myosin  in  meat  and  vitellin, 
found  in  the  yolk  of  the  egg,  and  some  of  the  proteids 
of  the  blood,  are  examples  of  globulins.  Albuminates 
are  casein-like  proteids  found  in  both  animal  and  vege- 
table foods.  They  are  supposed  to  be  proteins  that  are 
in  feeble  chemical  combination  with  acid  and  alkaline 
compounds,  and  they  are  sometimes  called  acid  and 
alkali  proteids.  Some  are  precipitated  from  their  solu- 
tions by  acids  and  others  by  alkalies.  Peas  and  beans 
contain  quite  large  amounts  of  a  casein-like  proteid 
called  legumin.  Proteoses  and  peptones  are  proteins 
soluble  in  water,  but  not  coagulated  by  heat.  They 
are  produced  from  other  proteids  by  ferment  action 
during  the  digestion  of  food  and  the  germination  of 
seeds,  and  are  often  due  to  the  changes  resulting  from 
the  action  of  the  natural  ferments  or  enzymes  inherent 
in  the  food  materials.  As  previously  stated,  the  insolu- 
ble proteids  are  present  in  far  the  largest  amount  of  any 


GENERAL    COMPOSITION    OF    FOODS  21 

of  the  nitrogenous  materials  of  foods.  Lean  meat  and 
the  gluten  of  wheat  and  other  grains  are  examples  of 
the  insoluble  proteids.  The  various  insoluble  proteids 
from  different  food  materials  each  has  its  own  compo- 
sition and  distinctive  chemical  and  physical  properties, 
and  from  each  a  different  class  and  percentage  amount 
of  derivative  products  are  obtained.1  While  in  general 
it  is  held  that  the  various  proteins  have  practically  the 
same  nutritive  value,  it  is  possible  that  because  of  differ- 
ences in  structural  composition  and  the  products  formed 
during  digestion  there  may  exist  notable  differences  in 
nutritive  value.  During  digestion  the  insoluble  pro- 
teids undergo  an  extended  series  of  chemical  changes. 
They  are  partially  oxidized,  and  the  nitrogenous  portion 
of  the  molecule  is  eliminated  mainly  in  the  form  of 
amids,  as  urea.  The  insoluble  proteins  constitute  the 
main  source  of  the  nitrogenous  food  supply  of  both 
humans  and  animals. 

20.  Crude  Protein.  —  In  the  analysis  of  foods,  the 
term  "crude  protein"  is  used  to  designate  the  total 
nitrogenous  compounds  considered  collectively;  it  is 
composed  largely  of  protein,  but  also  includes  the 
amids,  alkaloids,  and  albuminoids.  "  Crude  protein " 
and  "total  nitrogenous  compounds"  are  practically 
synonymous  terms.  The  various  proteins  all  contain 
about  1 6  per  cent  of  nitrogen  ;  that  is,  one  part  of  nitro- 
gen is  equivalent  to  6.25  parts  of  protein.  In  analyzing 
a  food  material,  the  total  organic  nitrogen  is  determined 


22         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

and  the  amount  multiplied  by  6.25  to  obtain  the  crude 
protein.  In  some  food  materials},  as  cereals,  the  crude 
protein  is  largely  pure  protein,  while  in  others,  as  pota- 
toes, it  is  less  than  half  pure  protein,  the  larger  portion 
being  amids  and  other  compounds.  In  comparing  the 
crude  protein  content  of  one  food  with  that  of  another, 
the  nature  of  both  proteids  should  be*considered  and  also 
the  amounts  of  non-proteid  constituents.  The  factor 
6.25  for  calculating  the  protein  equivalent  of  foods  is 
not  strictly  applicable  to  all  foods.  For  example,  the 
proteids  of  wheat  —  gliadin  and  glutenin  —  contain  over 
1 8  per  cent  of  nitrogen,  making  the  nitrogen  factor 
about  5.68  instead  of  6.25.  If  wheat  contains  2  per 
cent  of  nitrogen,  it  is  equivalent  to  12.5  per  cent  of 
crude  protein,  using  the  factor  6.25  ;  or  to  11.4,  using 
the  factor  5.7.  The  nitrogen  content  of  foods  is  abso- 
lute;  the  protein  content  is  only  relative.9 

21.  Food  Value  of  Protein.  —  Because  of  its  complex- 
ity in  composition,  protein  is  capable  of  being  used  by 
the  body  in  a  greater  variety  of  ways  than  starch,  sugar, 
or  fat.  In  addition  to  producing  heat  and  energy,  pro- 
tein serves  the  unique  function  of  furnishing  material 
for  the  construction  of  new  muscular  tissue  and  the  repair 
of  that  which  is  worn  out.  It  is  distinctly  a  tissue-build- 
ing nutrient.  It  also  enters  into  the  composition  of  all 
the  vital  fluids  of  the  body,  as  the  blood,  chyme,  chyle, 
and  the  various  digestive  fluids.  Hence  it  is  that  pro- 
tein is  required  as  a  nutrient  by  the  animal  body,  and  it 


GENERAL    COMPOSITION    OF    FOODS  23 

cannot  be  produced  from  non-nitrogenous  compounds. 
In  vegetable  bodies,  the  protein  can  be  produced  syn- 
thetically from  amids,  which  in  turn  are  formed  from 
ammonium  compounds.  While  protein  is  necessary  in 
the  ration,  an  excessive  amount  should  be  avoided. 
When  there  is  more  than  is  needed  for  functional  pur- 
poses, it  is  used  for  heat  and  energy,  and  as  foods  rich 
in  protein  are  usually  the  most  expensive,  an  excess  adds 
unnecessarily  to  the  cost  of  the  ration.  Excess  of  pro- 
tein in  the  ration  may  also  result  in  a  diseased  condition, 
due  to  imperfect  elimination  of  the  protein  residual  prod* 
ducts  from  the  body.10 

22.  Albuminoids  differ  from  proteids  in  general  com- 
position and,  to  some  extent,  in  nutritive  value.     They 
are  found  in  animal   bodies    mainly  in  the  connective 
tissue  and  in  the  skin,  hair,  and  nails.    Some  of  the  albu- 
minoids, as  nuclein,  are  equal  in  food  value  to  protein, 
while  others   have   a   lower   food   value.     In   general, 
albuminoids  are  capable  of    conserving  the   protein  of 
the  body,  and  hence  are  called  "protein  sparers,"  but 
they  cannot  in  every  way  enter  into  the  composition  of 
the  body,  as  do  the  true  proteins. 

23.  Amids    and    Amines.  —  These    are    nitrogenous 
compounds  of  simpler  structure  than  the  proteins  and 
albuminoids.      They   are    sometimes    called    compound 
ammonia  in  that  they  are  derived  from  ammonia  by  the  re- 
placement of  one  of  the  hydrogen  atoms  with  an  organic 
radical.     In  plants,  amids  are  intermediate  compounds 


24        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

in  the  production  of  the  proteids,  and  in  some  vegetables 
a  large  portion  of  the  nitrogen  js  amids.  In  animal 
bodies  amids  are  formed  during  oxidation,  digestion, 
and  disintegration  of  proteids.  It  is  not  definitely  known 
whether  or  not  a  protein  in  the  animal  body  when 
broken  down  into  amid  form  can  again  be  reconstructed 
into  protein.  The  amids  have  a  lower  food  value  than 
the  proteids  and  albuminoids.  It  is  generally  held  that, 
to  a  certain  extent,  they  are  capable,  when  combined 
with  proteids,  of  preventing  rapid  conversion  of  the 
body  proteid  into  soluble  form.  When  they  are  used 
in  large  amounts  in  a  ration,  they  tend  to  hasten  oxida- 
tion rather  than  conservation  of  the  proteids. 

24.  Alkaloids.  —  In  some  plant  bodies  there  are  small 
amounts  of  nitrogenous  compounds  called  alkaloids. 
They  are  not  found  to  any  appreciable  extent  in  food 
plants.  The  alkaloids,  like  ammonia,  are  basic  in 
character  and  unite  with  acids  to  form  salts.  Many 
medicinal  plants  owe  their  value  to  the  alkaloids  which 
they  contain.  In  animal  bodies  alkaloids  are  formed 
when  the  tissue  undergoes  fermentation  changes,  and 
also  during  disease,  the  products  being  known  as 
ptomaines.  Alkaloids  have  no  food  value,  but  act 
physiologically  as  irritants  on  the  nerve  centers,  making 
them  useful  from  a  medicinal  rather  than  from  a  nutri- 
tive point  of  view.  To  medical  and  pharmaceutical 
students  the  alkaloids  form  a  very  important  group  of 
compounds. 


GENERAL  COMPOSITION  OF  FOODS         25 

25.  General  Relationship  of  the  Nitrogenous  Com- 
pounds.— Among  the  various  subdivisions  of  the  nitroge- 
nous compounds  there  exists  a  relationship  similar  to 
that  among  the  non-nitrogenous  compounds.  From 


1  2  3456 

FIG.  5.  — GRAPHIC  COMPOSITION  OF  FLOUR. 
I,  flour;  2,  starch;  3,  gluten;  4,  water;  5,  fat;  6,  ash. 

proteids,  amids  and  alkaloids  may  be  formed,  just  as 
invert  sugars  and  their  products  are  formed,  from 
sucrose.  Although  glucose  products  are  derived  from 
sucrose,  it  is  not  possible  to  reverse  the  process  and 
obtain  sucrose  or  cane  sugar  from  starch.  So  it  is  with 
proteins,  while  the  amid  may  be  obtained  from  the 


26         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

proteid  in  animal  nutrition,  as  far  as  known  the  process 
cannot  be  reversed  and  proteids  tje  obtained  from  amids. 
In  the  construction  of  the  protein  molecule  of  plants, 
nitrogen  is  absorbed  from  the  soil  in  soluble  forms,  as 
compounds  of  nitrates  and  nitrites  and  ammonium  salts. 
These  are  converted,  first,  into  amids  and  then  into 
proteids.  In  the  animal  body  just  the  reverse  of  this 
process  takes  place, — the  protein  of  the  food  under- 
goes a  series  of  changes,  and  is  finally  eliminated  from 
the  body  as  an  amid,  which  in  turn  undergoes  oxidation 
and  nitrification,  and  is  converted  into  nitrites,  nitrates, 
and  ammonium  salts.  These  forms  of  nitrogen  are  then 
ready  to  begin  again  in  plant  and  animal  bodies  the 
same  cycle  of  changes.  Thus  it  is  that  nitrogen  may 
enter  a  number  of  times  into  the  composition  of  plant 
and  animal  tissues.  Nature  is  very  economical  in  her 
use  of  this  element.5 


CHAPTP:R  n 

CHANGES  IN  COMPOSITION  OF   FOODS   DURING  COOK- 
ING AND  PREPARATION 

26.  Raw  and    Cooked    Foods  Compared.  —  Raw  and 

cooked  foods  differ  in  chemical  composition  mainly  in 
the  content  of  water.  The  amount  of  nutrients  on  a 
dry  matter  basis  is  practically  the  same,  but  the  struc- 
tural composition  is  affected  by  cooking,  and  hence  it 
is  that  a  food  prepared  for  the  table  often  differs 
appreciably  from  the  raw  material.  Cooked  meat,  for 
example,  has  not  the  same  percentage  and  structural 
composition  as  raw  meat,  although  the  difference  in 
nutritive  value  between  a  given  weight  of  each  is  not 
large.  During  cooking,  foods  are  acted  upon  chemi- 
cally, physically,  and  bacteriologically,  and  it  is  usually 
the  joint  action  of  these  three  agencies  that  brings  about 
the  desirable  changes  incident  to  their  preparation  for 
the  table. 

27.  Chemical  Changes  during  Cooking.  —  Each  of  the 
chemical  compounds  of  which  foods   are   composed  is 
influenced  to   a    greater  or  less   extent   by  heat    and 
modified  in  composition.     The  chemistry  of  cooking  is 
mainly  a  study  of  the  chemical  changes  that  take  place 
when  compounds,  as  cellulose,  starch,  sugar,  pectin,  fat, 

27 


28         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

and  the  various  proteids,  are  subjected  to  the  joint 
action  of  heat,  moisture,  air,  and  ferments.  The  changes 
which  affect  the  cellulose  are  physical  rather  than 
chemical.  A  slight  hydration  of  the  cellular  tissue, 
however,  doe's  take  place.  In  human  foods  cellulose  is 
not  found  to  any  appreciable  extent.  Many  vegetables, 
as  potatoes,  which  are  apparently  composed  of  cellular 
substances,  contain  but  little  true  cellulose.  Starch,  as 
previously  stated,  undergoes  hydration  in  the  presence 
of  water,  and,  at  a  temperature  of  120°  C,  is  converted 
into  dextrine.  At  a  higher  temperature  disintegration 
of  the  starch  molecule  takes  place,  with  the  formation 
of  carbon  monoxid,  carbon  dioxid,  and  water,  and  the 
production  of  a  residue  richer  in  carbon  than  is  starch. 
On  account  of  the  moisture,  the  temperature  in  many 
cooking  operations  is  not  sufficiently  high  for  changes 
other  than  hydration  and  preliminary  dextrinizing.  In 
Chapter  XI  is  given  a  more  extended  account  of  the 
changes  affecting  starch  which  occur  in  bread  making. 

During  the  cooking  process  sugars  undergo  inversion 
to  a  slight  extent.  That  is,  sucrose  is  converted  into 
levulose  and  dextrose  sugars.  At  a  higher  temperature, 
sugar  is  broken  up  into  its  constituents  —  water  and 
carbon  dioxide.  The  organic  acids  which  many  fruits 
and  vegetables  contain  hasten  the  process  of  inversion. 
When  sugar  is  subjected  to  dry  heat,  it  becomes  a  brown, 
caramel-like  material  sometimes  called  barley  sugar. 
During  cooking,  sugars  are  not  altered  in  solubility  or 
digestibility ;  starches,  however,  are  changed  to  a  more 


CHANGES    IN    FOODS    DURING    COOKING  29 

soluble  form,  and  pectin  —  a  jelly-like  substance — is 
converted  from  a  less  to  a  more  soluble  condition,  as 
stated  in  Chapter  I.  Changes  incident  to  the  cooking 
of  fruits  and  vegetables  rich  in  pectin,  as  in  the  making 
of  jellies,  are  similar  to  those  which  take  place  in  the 
last  stages  of  ripening. 

The  fats  are  acted  upon  to  a  considerable  extent  by 
heat.  Some  of  the  vegetable  oils  undergo  slight  oxida- 
tion, resulting  in  decreased  solubility  in  ether,  but  since 
there  is  no  volatilization  of  the  fatty  matter,  it  is  a 
change  that  does  not  materially  affect  the  total  fuel 
value  of  the  food.11 

There  is  a  general  tendency  .for  the  proteids  to  be- 
come less  soluble  by  the  action  of  heat,  particularly  the 
albumins  and  globulins.  The  protein  molecule  dissoci- 
ates at  a  high  temperature,  with  formation  of  volatile 
products,  and  therefore  foods  rich  in  protein  should  not 
be  subjected  to  extreme  heat,  as  losses  of  food  value 
may  result.  During  cooking,  proteids  undergo  hydra- 
tion,  which  is  necessary  and  preliminary  to  digestion, 
and  the  heating  need  be  carried  only  to  this  point,  and 
not  to  the  splitting  up  of  the  molecule.  Prolonged  high 
temperature  in  the  cooking  of  proteids  and  starches  is 
unnecessary  in  order  to  induce  the  desired  chemical 
changes.  When  these  nutrients  are  hydrated,  they  are 
in  a  condition  to  undergo  digestion,  without  the  body 
being  compelled  to  expend  unnecessary  energy  in  bring- 
ing about  this  preliminary  change.  Hence  it  is  that, 
while  proper  cooking  does  not  materially  affect  the  total 


30        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


digestibility  of  proteids  or  starches,  it  influences  ease  of 
digestion,  as  well  as  conserves  available  energy,  thereby 
making  more  economical  use  of  these  nutrients. 

28.  Physical  Changes.  —  The  mechanical  structure  of 
foods  is  influenced  by  cooking  to  a  greater  extent  ^than 
is  the  chemical  composition.  One  of  the  chief  objects 
of  cooking  is  to  bring  the  food  into  better  mechanical 
condition  for  digestion.12  Heat  and  water  cause  partial 
disintegration  of  both  animal  and  vegetable  tissues. 
The  cell-cementing  materials  are  weakened,  and  a  sof- 
tening of  the  tissues 
results.  Often  the 
action  extends  still 
further  in  vegetable 
foods,  resulting  in 
disintegration  of  the 
individual  starch 
granules.  When 
foods  are  subjected 
to  dry  heat,  the  mois- 
ture they  contain  is 
converted  into 
steam,  which  causes 

FIG.  6.  — CELLS  OF  A  PARTIALLY  COOKED      bursting  of   the    tis- 
POTATO.     (After  KONIG.)  A 

sues.  A  good  ex- 
ample of  this  is  the  popping  of  corn.  Heat  may 
result,  too,  in  mechanical  removal  of  some  of  the 
nutrients,  as  the  fats,  which  are  liquefied  at  temperatures 


CHANGES    IN    FOODS    DURING    COOKING 


ranging  from  100°  to  200°  F.  Many  foods  which  in  the 
raw  state  contain  quite  large  amounts  of  fat,  lose  a  por- 
tion mechanically  during  cooking,  as  is  the  case  with 
bacon  when  it  is  cut  in  thin  slices  and  fried  or  baked 
until  crisp.  When  foods  are  boiled,  the  natural  juices 
being  of  somewhat  different  density  from  the  water  in 
which  they  are  cooked,  slight  osmotic  changes  occur. 
There  is  a  tendency  toward  equalization  of  the  compo- 
sition of  the  juices  of  the  food  and  the  water  in  which 
they  are  cooked.  In  order  to  achieve  the  best  mechani- 
cal effects  in  cooking,  high  temperatures  are  not  neces- 
sary, except  at  first  for  rupturing  the  tissues  ;  softening 
of  the  tissues  is  best 
effected  by  prolonged 
and  slow  heat.  At  a 
higher  temperature 
many  of  the  volatile 
and  essential  oils  are 
lost,  while  at  lower 
temperatures  these 
are  retained  and  in 
some  instances 
slightly  developed. 
The  cooking  should 
be  sufficiently  pro- 
longed and  the  tem- 
perature high  enough 
to  effectually  disintegrate  and  soften  all  of  the  tissues, 
but  not  to  cause  extended  chemical  changes. 


FIG.  7._  CELLS  OF  RAW  POTATO,  SHOWING 
STARCH  GRAINS.    (After  KONIG.) 


32         HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

There  is  often  an  unnecessarily  large  amount  of  heat 
lost  through  faulty  construction  of  stoves  and  lack  of 
judicious  use  of  fuels,  which  greatly  enhances  the  cost 
of  preparing  foods.  Ovens  are  frequently  coated  with 
deposits  of  soot ;  this  causes  the  heat  to  be  thrown  out 
into  the  room  or  lost  through  the  chimney,  rather  than 
utilized  for  heating  the  oven.  In  an  ordinary  cook  stove 
it  is  estimated  that  less  than  7  per  cent  of  the  heat  and 
energy  of  the  fuel  is  actually  employed  in  bringing  about 
physical  and  chemical  changes  incident  to  cooking.13 

29.  Bacteriological  Changes. — The  bacterial  organ- 
isms of  foods  are  destroyed  in  the  cooking,  provided  a 
.temperature  of  150°  F.  is  reached  and  maintained  for 
several  minutes.  The  interior  of  foods  rarely  reaches 
a  temperature  above  200°  F.,  because  of  the  water  they 
contain  which  is  not  completely  removed  below  212°. 
One  of  the  chief  objects  in  cooking  food  is  to  render 
it  sterile.  Not  only*  do  bacteria  become  innocuous 
through  cooking,  but  various  parasites,  as  trichina  and 
tapeworm,  are  destroyed,  although  some  organisms  can 
live  at  a  comparatively  high  temperature.  Cooked  foods 
are  easily  re-inoculated,  in  some  cases  more  readily  than 
fresh  foods,  because  they  are  in  a  more  disintegrated 
condition. 

In  many  instances  bacteria  are  of  material  assistance 
in  the  preparation  of  foods,  as  in  bread  making,  butter 
making,  curing  of  cheese,  and  ripening  of  meat.  All 
the  chemical  compounds  of  which  foods  are  composed 


CHANGES    IN    FOODS    DURING    COOKING  33 

are  subject  to  fermentation,  each  compound  being  acted 
upon  by  its  special  ferment  body."  Those  which  convert 
the  proteids  into  soluble  form,  as  the  peptonizing  fer- 
ments, have  no  action  upon  the  carbohydrates.  A  cycle 
of  bacteriological  changes  often  takes  place  in  a  food 
material,  one  class  of  ferments  working  until  their  prod- 
ucts accumulate  to  such  an  extent  as  to  prevent  their 
further  activity,  and  then  the  process  is  taken  up  by 
others,  as  they  find  the  conditions  favorable  for  devel- 
opment. This  change  of  bacterial  flora  in  food  mate- 
rials is  akin  to  the  changes  in  the  vegetation  occupying 
soils.  In  each  case,  there  is  a  constant  struggle  for 
possession.  Bacteria  take  a  much  more  important  part 
in  the  preparation  of  foods  than  is  generally  considered. 
As  a  result  of  their  workings,  various  chemical  products, 
as  organic  acids  and  aromatic  compounds,  are  produced. 
The  organic  acids  chemically  unite  with  the  nutrients  of 
foods,  changing  their  composition  and  physical  proper- 
ties. Man  is,  to  a  great  extent,  dependent  upon  bacterial 
action.  Plant  life  also  is  dependent  upon  the  bacterial 
changes  which  take  place  in  the  soil  and  in  the  plant  tis- 
sues. The  stirring  of  seeds  into  activity  is  apparently 
due  to  enzymes  or  soluble  ferments  which  are  inherent 
in  the  seed.  A  study  of  the  bacteriological  changes 
which  foods  undergo  in  their  preparation  and  digestion 
more  properly  belongs  to  the  subject  of  bacteriology, 
and  in  this  work  only  brief  mention  is  made  of  some  of 
the  more  important  parts  which  microorganisms  take 
in  the  preparation  of  foods.  ' 


34        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

30.  Insoluble  Ferments.  —  Insoluble  ferments  are  mi- 
nute, plant-like  bodies  of  definite  form  and  structure,  and 

can  be  studied  only  with  the  micro- 
scope.1 They  are  developed  from 
spores  or  seeds,  or  from  the  split- 
ting or  budding  of  the  parent  cells. 
Under  suitable  conditions  they  mul- 

FIG.  s.- LACTIC  ACID    ^  raPidlY>  deriving  the  energy  for 
BACTERIA,      MUCH    their  life  processes  from  the  chemical 
RussAERLGLE)D'     (AftCr    changes  which  they  induce.     For  ex- 
ample,  in   the   souring   of   milk   the 
milk  sugar  is  changed  by  the  lactic  acid  ferments  into 
lactic  acid.     In  causing  chemical  changes,  the  ferment 
gives  none  of  its  own  material  to  the  reacting  substance. 
These  ferment  bodies  undergo  life  processes  similar  to 
plants  of  a  higher  order. 

All  foods  contain  bacteria  or  ferments.  In  fact,  it  is 
impossible  for  a  food  stored  and  prepared  under  ordi- 
nary conditions,  unless  it  has  been  specially  treated,  to 
be  free  from  them.  Some  of  them  are  useful,  some  are 
injurious,  while  others  are  capable  of  producing  disease. 
The  objectionable  bacteria  are  usually  destroyed  by  the 
joint  action  of  sunlight,  pure  air,  and  water. 

31.  Soluble  Ferments.  —  Many  plant  and  animal  cells 
have  the  power  of  secreting  substances  soluble  in  water 
and  capable  of   producing  fermentation  changes  ;    to 
these  the  term  "soluble  ferments,"  or  " enzymes/'  is  ap- 
plied.    These  ferments  have  not  a  cell  structure  like  the 


CHANGES    IN    FOODS    DURING   COOKING  35 

organized  ferments.  When  germinated  seed,  as  malted 
barley,  is  extracted,  a  soluble  and  highly  nitrogenous 
substance,  called  the  diastase  ferment,  is  secured  that 
changes  starch  into  soluble  forms.  The  soluble  fer- 
ments induce  chemical  change  by  causing  molecular 
disturbance  or  splitting  up  of  the  organic  compounds, 
resulting  in  the  production  of  derivative  products.  They 
take  an  important  part  in  animal  and  plant  nutrition, 
as  by  their  action  insoluble  compounds  are  brought  into 
a  soluble  condition  so  they  can  be  utilized  for  nutritive 
purposes.  In  many  instances  ferment  changes  are  due 
to  the  joint  action  of  soluble  and  insoluble  ferments. 
The  insoluble  ferment  secretes  an  enzyme  which  in- 
duces a  chemical  change,  modified  by  the  further  action 
of  the  soluble  ferment.  Many  of  the  enzymes  carry  on 
their  work  at  a  low  temperature,  as  in  the  curing  of 
meat  and  cheese  in  cold  storage.14 

32.  General  Relationship  of  Chemical,  Physical,  and 
Bacteriological   Changes.  —  It  cannot  be  said  that  the 
beneficial   results    derived  rfrom  the  cooking  of    foods 
are  due  to  either  chemical,  physical,  or  bacteriological 
change  alone,  .but  to  the  joint  action  of  the  three.     In 
order  to  secure  a  chemical  change,  a  physical  change 
must  often  precede,  and  a  bacteriological  change  can- 
not take  place  without  causing  a  change  in  chemical  com- 
position ;  the  three  are  closely  related  and  interdependent. 

33.  Esthetic  Value  of  Foods.  —  Foods  should  be  not 
only  of  good  physical  texture  and  contain  the  requisite 


36        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


nutrients,  but  they  should  also  be  pleasing  to  the  eye 
and  served  in  the  most  attractive  manner.  Some  foods 
owe  a  part  of  their  commercial  value  to  color,  and  when 
they  are  lacking  in  natural  color  they  are  not  consumed 
with  a  relish.  There  is  no  objection  to  the  addition  of 
coloring  matter  to  foods,  provided  it  is  of  a  non-injurious 
character  and  does  not  affect  the  amount  of  nutrients, 
and  that  its  presence  and  the  kind  of  coloring  material 
are  made  known.  Some  foods  contain  objectionable 
colors  which  are  eliminated  during  the  process  of  manu- 
facture, as  in  the  case  of  sugar  and  flour.  As  far  as  re- 
moval of  coloring  matter  from  foods  during  refining  is 
concerned,  there  can  be  no  objection,  so  long  as  no  inju- 
rious reagents  or  chemicals  are  retained,  as  the  removal  of 
the  color  in  no  way  affects  the  nutritive  value  or  permits 
fraud,  but  necessitates  higher  purification  and  refining. 
The  use  of  chemicals  and  reagents  in  the  preparation  and 
refining  of  foods  is  considered  permissible  in  all  cases 
where  the  reagents  are  removed  by  subsequent  processes. 
In  the  food  decisions  of  the  United  States  Department 
of  Agriculture,  it  is  stated :  "  Not  excluded  under  this  pro- 
vision are  substances  properly  used  in  the  preparation 
of  food  products  for  clarification  or  refining  and  elimi- 
nated in  the  further  process  of  manufacture."  15 


CHAPTER   III 
VEGETABLE  FOODS 

34.  General  Composition.  —  Vegetable  foods,  with  the 
exception  of  cereals,  legumes,  and  nuts,  contain  a  smaller 
percentage  of  protein  than  animal  food  products.     They 
vary  widely  in  composition  and  nutritive  value;  in  some, 
starch  predominates,  while  in  others,  sugar,  cellulose, 
and    pectin  bodies   are   most  abundant.     The   general 
term  " vegetable  foods"  is  used  in  this  work  to  include 
roots,  tubers,  garden  vegetables,  cereals,  legumes,  and  all 
prepared  foods  of  vegetable  origin. 

35.  Potatoes   contain   about    75    per   cent   of    water 
and  25  per  cent  of  dry  matter,  the  larger  portion  being 
starch.     There  is  but  little  nitrogenous  material  in  the 
potato,  only  2.25  per  cent,  of  which  about  half  is  in  the 
form  of  proteids.     There  are  ten  parts  of  non-nitroge- 
nous substance  to  every  one  part  of  nitrogenous;    or, 
in  other  words,  the  potato  has  a  wide  nutritive  ratio, 
and   as   an    article    of  diet  needs  to  be   supplemented 
with  foods  rich  in  protein.     The  mineral  matter,  cellu- 

37 


HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


a, 


lar  tissue,  and  fat  in  potatoes  are  small  in  amount,  as 
are  also  the  organic  acids.  Mechanically  considered, 
the  potato  is  composed  of  three  parts,  —  outer  skin,  inner 
skin,  and  flesh.  The  layer  immediately  beneath  the  outer 
skin  is  slightly  colored,  and  is  designated  the  fibro-vascu- 

lar  layer.  The  outer  and  inner 
skins  combined  make  up  about 
10  per  cent  of  the  weight  of 
the  potato. 

A  large  portion  of  the  pro- 
tein of  the  potato  is  albumin, 
which  is  soluble  in  water. 
When  potatoes  are  peeled,  cut 
in  small  pieces,  and  soaked  in 
water  for  several  hours  before 
boiling,  80  per  cent  of  the  crude 
protein,  or  total  nitrogenous 
material,  is  extracted,  render- 
ing the  product  less  valuable 
as  food.  When  potatoes  are 
placed  directly  in  boiling  water,  the  losses  of  nitroge- 
nous compounds  are  reduced  to  about  7  per  cent,  and, 
when  the  skins  are  not  removed,  to  i  per  cent.  Di- 
gestion experiments  show  that  92  per  cent  of  the  starch 
and  72  per  cent  of  the  protein  are  digested.12  Com- 
pared with  other  foods,  potatoes  are  often  a  cheap  source 
of  non-nitrogenous  nutrients.  If  used  in  excessive 
amounts,  however,  they  have  a  tendency  to  make  the 
ration  unbalanced  and  too  bulky. 


FIG.  9.  —  TRANSVERSE  SECTION 
OF  POTATO.  (After  COWDEN 
and  BUSSARD.)  a,  skin ;  bt  cor- 
tical layer;  c,  outer  medullary 
layer;  d,  inner  medullary  layer. 


VEGETABLE  FOODS 


39 


MECHANICAL  COMPOSITION  OF  THE  POTATO 


Per  Cent 
IOO  O 

sy    r 

Inner  skin,  or  fibro-vascular  layer  *     

2-5 

8  c 

Flesh  

o*5 

80  o 

CHEMICAL  COMPOSITION  OF  THE  POTATO 


CARBOHYDRATES 

Crude 

Nitro- 

Water 

Pro- 

Fat 

gen- 
free- 

Fiber 

Ash 

tein 

extract 

Outer,  or  true  skin  .     . 

80.  1 

2.7 

0.8 

\. 

6 

1.8 

Inner    skin,   or    fibro- 

vascular  layer       .     . 

83.2 

2-3 

O.I 

12.6 

0.7 

i.i 

Flesh     

81.1 

2.O 

O.I 

15.7 

O.'* 

0.8 

Average  of  86  Ameri- 

can analyses  f      .     . 

78.0 

2.2 

O.I 

18. 

8 

0.9 

Average  of  118  Euro- 

pean analyses  f    .     . 

75.0 

2.1 

O.I 

21.0 

0.7 

i.i 

36.  Sweet  Potatoes  contain  more  dry  matter  than 
white  potatoes,  the  difference  being  due  mainly  to  the 
presence  of  about  6  per  cent  of  sugar.  There  is  approxi- 
mately the  same  starch  content,  but  more  fat,  protein, 

*  Including  a  small  amount  of  flesh. 

f  From  an  unpublished  compilation  of  analyses  of  American  food 
products. 

J  Konig,  "  Chemie  der  Nahrungs-  und  Genussmittel,"  3d  ed.,  II,  p.  626. 


40        HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

and  fiber.     As  a  food,  they  supply  a  large  amount  of 
non-nitrogenous  nutrients. 

37.  Carrots  contain  about  half  as  much  dry  matter  as 
potatoes,  and  half  of  the  dry  matter  is  sugar,   nearly 
equally  divided  between  sucrose  and  levulose,  or  fruit 
sugar.       Like  the  potato,  carrots  have    some    organic 
acids  and  a  relatively   small   amount  of   proteids.     In 
carrots  and  milk  there  is  practically  the  same  per  cent: 
of  water.     The  nutrients  in  each,  however,  differ  both 
as    to    kind   and    proportion.       Experiments     with   the 
cooking   of  carrots   show  that   if   a   large   amount   of 
water    is   used,    30   per   cent   or   more   of    the    nutri- 
ents, particularly  of  the  more  soluble  sugar  and  albu- 
min, are  extracted  and  lost  in  the  drain  waters.12     The 
color  of  the  carrot  is  due  to  the  non-nitrogenous  com- 
pound   carrotin,    C26H38.      Carrots    are   valuable    in    a 
ration  not  because  of  the  nutrients  they  supply,  but  for 
the  palatability  and  the    mechanical  action  which  the 
vegetable  fiber  exerts  upon  the  process  of  digestion. 

38.  Parsnips  contain  more  solid  matter  than  beets  or 
carrots,  of  which  3  to  4  per  cent  is  starch.     The  starch 
grains  are  very  small,  being   only  about  one  twentieth 
the  size  of  the  potato  starch  grains.     There  is  3  per  cent 
of  sugar  and  an  appreciable  amount  of  fat,  more  than 
in  any  other  of  the  vegetables  of  this  class,  and  seven 
times  as  much  as  in  the  potato.     The  mineral  matter  is 
of  somewhat  different  nature  from  that  in  potatoes ;  in 
parsnips  one  half  is  potash  and  one  quarter  phosphoric 


VEGETABLE  FOODS 


acid,  while  in  potatoes  three  quarters  are  potash  and 
one  fifth  phosphoric  acid. 

39.  Cabbage  contains  very  little  dry  matter,  usually 
less  than    10   per  cent.      It  is  proportionally  richer  in 
nitrogenous        com- 
pounds   than    many 

vegetables,  as  about 
two  of  the  ten  parts 
of  dry  matter  are 
crude  protein,  which 
makes  the  nutritive 
ratio  one  to  five. 
During  cooking  30 
to  40  per  cent  of 
the  nutrients  are 
extracted.  Cabbage 
imparts  to  the  ration 
bulk  but  compara- 
tively little  nutritive  material.  It  is  a  valuable  food 
adjunct,  particularly  used  raw,  as  in  a  salad,  when  it  is 
easily  digested  and  retains  all  of  the  nutrients.12 

40.  Cauliflower  has  much  the  same  general  composi- 
tion as  cabbage,  from  which  it  differs  mainly  in  mechan- 
ical structure. 

41.  Beets.  —  The  garden  beet  contains  a  little  more 
protein  than  carrots,  but  otherwise  has  about  the  same 
general  composition,  and  the  statements  made  in  regard 


FIG.  10. —  GRAPHIC  COMPOSITION  OF 
CABBAGE. 


42         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

to  the  losses  of  nutrients  in  the  cooking  of  carrots  and 
to  their  use  in  the  dietary  apply  also  to  beets. 

42.  Cucumbers    contain  about    4    per   cent    of    dry 
matter.     The    amount  of  nutrients   is    so    small    as   to 
scarcely  allow  them  to  be  considered  a  food.     They  are, 
however,  a  valuable  food  adjunct,  as  they  impart  palata- 
bility. 

43.  Lettuce  contains  about  7  per  cent  of  solids,  of 
which  1.5  is  protein  and  2.5  starch  and  sugar.     While 
low  in  nutrients,  it  is  high  in  dietetic  value,  because  of 
the  chlorophyll  which  it  contains.    It  has  been  suggested 
that  it  is  valuable,  too,  for  supplying  iron  in  an  organic 
form,   as   there  is  iron  chemically  combined  with  the 
chlorophyll. 

44.  Onions   are  aromatic   bulbs,  valuable   for   condi- 
mental    rather  than  nutritive   purposes.     They  contain 
essential  and  volatile  oils,  which  impart  characteristic 
odor  and  flavor.     In  the  onion  there  are  about  1.5  per 
cent  of   protein  and  9.5    per  cent  of   non-nitrogenous 
material.     Onions  are  often   useful  in  stimulating  the 
digestive  tract  to  action. 

45.  Spinach  is   a  valuable   food,  not   to   be   classed 
merely  as  a  relish.     Its  composition  is  interesting  ;  for, 
although  there  is  90  per  cent  water,  and  less  than  10 
per  cent  dry  matter,  it  still  possesses  high  food  value. 
Spinach  contains  2. 1  per  cent  crude  protein,  or  about  one 
part  to  every  four  parts  of  carbohydrates.     In  potatoes, 


VEGETABLE  FOODS 


43 


turnips,  and  beets  there  are  ten  or  more  parts  of  car- 
bohydrates to  every  one  part  of  protein. 

46.  Asparagus  is  composed  largely  of  water,  about 
93  per  cent.     The  dry  matter,  however,  is  richer  in  pro- 
tein than  that  of  many  vegetables.     Asparagus  contains, 
too,  an  amid  compound,  asparagin,  which  gives  some  of 
the  characteristics  to  the  vegetable. 

47.  Melons.  —  Melons  contain  from  8  to   10  percent 
of  dry  matter,  the  larger  portion  of  which  is  sugar  and 
allied  carbohydrates.     The  flavor  is  due  to  small  amounts 
of  essential  oils  and  to  organic  acids  associated  with 
the   sugars.     Melons  possess  condimental  rather  than 
nutritive  value. 

48.  Tomatoes. — The   tomato   belongs  to  the  night- 
shade family,  and  for  this  reason  was  long  looked  upon 

with  suspicion.  It  was 
first  used  for  ornamental 
purposes  and  was  called 
"  love-apple."  Gradu- 
ally, as  the  idea  of  its 
poisonous  nature  be- 
came dis- 
pelled, it 

grew  more  and  more 
popular  as  a  food,  until 
now  in  the  United  States 

it   is   one   of    the    most    common    garden   vegetables. 

It  contains  7  per  cent  of  dry  matter,  4  per  cent  of 


FIG.  ii. -GRAPHIC  COMPOSITION  OF 
TOMATO. 


44        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

which  is  sucrose,  dextrose,  and  levulose.  It  also  con- 
tains some  malic  acid,  and  a  small  amount  of  pro- 
teids,  amids,  cellulose,  and  coloring  material.  In  the 
canning  of  tomatoes,  if  too  much  of  the  juice  is  excluded, 
a  large  part  of  the  nutritive  material  is  lost,  as  the  sugars 
and  albumins  are  all  soluble  and  readily  removed.16  If 
the  seeds  are  objectionable,  they  may  be  removed  by 
straining  and  the  juice  added  to  the  fleshy  portion.  The 
product  then  has  a  higher  nutritive  value  than  if  the 
juice  had  been  discarded  with  the  seeds. 

49.  Sweet  Corn.  —  Fresh,  soft,  green,  sweet  corn  con- 
tains about  75  per  cent  of  water.     The  dry  matter  is 
half  starch  and  one  quarter  sugar.     The  protein  content 
makes  up  nearly  5  per  cent,  a  larger  proportional  amount 
than  is  found  in  the  ripened  corn,  due  to  the  fact  that 
the  proteids  are  deposited  in  the  early  stages  of  growth 
and  the  carbohydrates  mainly  in  the  last  stages.     Sweet 
corn  is  a  vegetable  of  high  nutritive  value  and  palata- 
bility. 

50.  Eggplant  contains  a  high  per  cent  of  water, — 90 
per  cent.     The  principal  nutrients,  are  starch  and  sugar, 
which  make  up  about  half  the  weight  of  the  dry  matter.. 
It  does  not  itself  supply  a  large  amount  of  nutrients,' 
but  the  way  in  which  it  is  prepared,  by  combination  with 
butter,  bread  crumbs,  and  eggs,  makes  it  a  nutritious  and 
palatable  dish,  the  food  value  being  derived  mainly  from 
the  materials  with  which  it  is  combined,  the  eggplant 
giving  the  flavor  and  palatability. 


VEGETABLE    FOODS  45 

51.  Squash   and   Pumpkin.  —  Squash  has  much  the 
same  general  composition  and  food  value  as  beets  and 
carrots,  although  it  belongs  to  a  different  family.     Pump- 
kins contain  less  dry  matter  than  squash.     The  dry  mat- 
ter of  both  is  composed  largely  of  starch  and  sugar  and, 
like  many  other  of  the  vegetables,  they  are  often  com- 
bined with  food  materials  containing  a  large  amount  of 
nutrients,  as  in  pumpkin  and  squash  pies,  where  the  food 
value  is  derived  mainly  from  the  milk,  sugar,  eggs,  flour, 
and  butter  or  other  shortening  used. 

52.  Celery.  —  The   dry  matter  of    celery  is  compar- 
atively   rich    in    nitrogenous    material,    although    the 
amount  is  small,  and  the  larger  proportion  is   in   non- 
proteid  form.     When   grown  on   rich   soil,  celery  may 
contain  an  appreciable  quantity  of  nitrates  and  nitrites, 
which  have  not  been  converted  into  amids  and  proteids. 
The  supposed  medicinal  value  is  probably  due  to  the 
nitrites  which  are  generally  present.     Celery  is  valuable 
from  a  dietetic  rather  than  a  nutritive  point  of  view.  , 

53.  Sanitary  Condition  of  Vegetables.  —  The  conditions 
under  which  vegetables  are  grown  have  much  to  do  with 
their  value,  particularly  from  a  sanitary  point  of  view. 
Uncooked  vegetables  often  cause  the  spread  of  diseases, 
particularly  those,  as  cholera  and  typhoid,  affecting  the 
digestive  tract.     Particles  of  dirt  containing  the  disease- 
producing  organisms  adhere  to  the  uncooked  vegetable 
and  find  their  way  into  the  digestive  tract,  where  the  bac- 
teria undergo  incubation.     When  sewage  has  been  used 


46         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

for  fertilizing  the  land,  as  in  sewage  irrigation,  the  vege- 
tables are  unsound  from  a  sanitary  point  of  view.  Such 
vegetables  should  be  thoroughly  cleaned  and  also  well 
cooked,  in  order  to  render  them  sterile.  Vegetables  to 
be  eaten  in  the  raw  state  should  be  dipped  momentarily 
into  boiling  water,  to  destroy  the  activity  of  the  germs 
present  upon  the  surface.  They  may  then  be  immedi- 
ately immersed  in  ice-cold  water,  to  preserve  the  crisp- 
ness. 

54.  Miscellaneous  Compounds  in  Vegetables.  —  In  ad- 
dition to  the  general  nutrients  which  have  been  discussed, 
many  of  the  vegetables  contain  some  tannin,  glucosides, 
and  essential  oils ;  and  occasionally  those  grown  upon 
rich  soils  have  appreciable  amounts  of    nitrogen  com- 
pounds, as  nitrates  and  nitrites,  which  have  not  been 
built  up  into  proteids.     Vegetables  have  a  unique  value 
in  the  dietary,  and  while  as  a  class  they  contain  small 
amounts  of  nutrients,  they  are  indispensable  for  promot- 
ing health  and  securing  normal  digestion  of  the  food. 

55.  Canned  Vegetables.  — When  sound  vegetables  are 
thoroughly  cooked  to  destroy  ferments,  and  then  sealed 
in  cans  while  hot,  they  can   be   kept  for   a   long  time 
without   any    material   impairment   of   nutritive    value. 
During  the  cooking  process  there  is  lost  a  part  of  the 
essential  oils,  which  gives  a  slightly  different  flavor  to 
the  canned  or  tinned  goods.17     In  some  canned  vege- 
tables  preservatives   are   used,   but  the  enactment  and 
enforcement  of  national  and  state   laws   have   greatly 


VEGETABLE  FOODS  47 

reduced  their  use.  When  the  cans  are  made  of  a  poor 
quality  of  tin,  or  the  vegetables  are  of  high  acidity, 
some  of  the  metal  is  dissolved  in  sufficient  quantity  to 
be  objectionable  from  a  sanitary  point  of  view.18 

56.  Edible  Portion  and  Refuse  of  Vegetables.  —  Many 
vegetables  have  appreciable  amounts  of  refuse,19  or 
non-edible  parts,  as  skin,  pods,  seeds,  and  pulp,  and  in 
determining  the  nutritive  value,  these  must  be  consid- 
ered, as  in  some  cases  less  than  50  per  cent  of  the 
weight  of  the  material  is  edible  portion,  which  propor- 
tionally increases  the  cost  of  the  nutrients.  Ordinarily, 
the  edible  part  is  richer  in  protein  than  the  entire 
material  as  purchased.  In  some  cases,  however,  the 
refuse  is  richer  in  protein,  but  the  protein  is  in  a  less 
available  form.  See  comparison  of  potatoes  and  potato 
skins. 


CHAPTER   IV 
FRUITS,  FLAVORS,  AND  EXTRACTS 

57.  General  Composition.  —  Fruits  are  characterized 
by  containing  a  large  amount  of  water  and  only  a  small 
amount  of  dry  matter,  which  is  composed  mainly  of 
sugar  and  non-nitrogenous  compounds.  Fruits  contain 
but  little  fatty  material  and  protein.  A  large  portion 
of  the  total  nitrogen  is  in  the  form  of  amid  compounds. 
Organic  acids,  as  citric,  tartaric,  and  malic,  are  found 
in  all  fruits,  and  the  essential  oils  form  a  characteristic 
feature.  The  taste  of  fruits  is  due  mainly  to  the  blend- 
ing of  the  various  organic  acids,  essential  oils,  and 
sugars.  Although  fruits  contain  a  high  per  cent  of 
water,  they  are  nevertheless  valuable  as  food.20  The 
constituents  present  to  the  greatest  extent  are  sugars 
and  acids.  The  sugar  is  not  all  like  the  common  granu- 
lated sugar,  but  in  ripe  fruits  a  part  is  in  the  form 
known  as  levulose  or  fruit  sugar,  which  is  two  and  a 
half  times  sweeter  than  granulated  sugar.  Sugars  are 
valuable  for  heat-  and  fat-producing  purposes,  but  not 
for  muscle  repairing.  Proteids  are  the  muscle-forming 
nutrients.  The  organic  acids,  as  malic  acid  in  apples, 
citric  acid  in  lemons  and  oranges,  and  tartaric  acid  in 
grapes,  have  characteristic  medicinal  properties.  The 


FRUITS,    FLAVORS,    AND    EXTRACTS 


49 


sugar,  proteid,  and  acid  content  of  some  of  our  more 

common  fruits  is  given  in  the  following  table  :21 

• 

COMPOSITION  OF  FRUITS 


WATER 

PROTEIDS 

SUGAR 

ACID  IN 
JUICE 

KIND  OF 
ACID 

Per  Cent 

Per  Cent 

Per  Cent 

Per  Cent 

Apples  (Baldwin) 

85.0 

0.50 

10.75 

0.92 

Malic 

Apples,  sweet    .     . 

86.0 

o  50 

11.75 

0.20 

Malic 

Blackberries      .     . 

88.9 

o  90 

II  50 

0.75 

Malic 

Currants  .... 

86.0 

— 

i.96 

5.80 

Tartaric 

Grapes     .... 

83  o 

1.50 

10  to  i  6 

1.2  to  5 

Tartaric 

Strawberries 

90.8 

0.95 

5-36 

1.40 

Malic 

Oranges   .... 

85.0 

1.  10 

IOOO 

1.30 

Citric 

Lemons    

84.0 

0.95 

2.00 

7.20 

Citric 

In  addition  to  sugars,  acids,  and  proteids,  there  are  a 
great  many  other  compounds  in  fruits.  Those  which 
give  the  characteristic  taste  are  called  essential  or  vola- 
tile oils. 

58.  Food  Value.  —  When  the  nutrients  alone  are  con- 
sidered, fruits  appear  to  have  a  low  food  value,  but  they 
should  not  be  judged   entirely  on   this  basis,   because 
they  impart  palatability  and  flavor  to  other  foods  and 
exercise  a  favorable  influence  upon  the  digestive  process. 
In  the  human  ration  fruits  are  a  necessary  adjunct. 

59.  Apples.  —  Apples  vary  in  composition  with  the 
variety  and    physical   characteristics   of   the  fruit.     In 
general  they  contain  from  10  to  16  per  cent  of  dry  mat- 
ter, of  which  75  per  cent,  or  more,  is  sugar  or  allied 


5<D         HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 


carbohydrates.  Among  the 
organic  acids  malic  pre- 
dominates, and  the  acidity 
ranges  from  o.  i  to  0.8  per 
cent.  Apples  contain  but 
little  protein,  less  than  i 
per  cent.  There  is  some 
pectin,  or  jelly-like  sub- 
stance closely  related  to 
the  carbohydrates.  The 
flavor  of  the  apple  varies 
with  the  content  of  sugar, 
organic  acids,  and  essen-  • 

tial  oils.    During  storage  some  apples  appear  to  undergo 

further   ripening,  resulting  in  partial   inversion  of  the 

sucrose,  and  there  is  a 

slight   loss  of  weight, 

due  to  the  formation  of 

carbon    dioxid.       The 

apple  is  an  important 

and    valuable    adjunct 

to  the  dietary.22 


FIG.  12.  — GRAPHIC  COMPOSITION 
OF  APPLE. 


60.  Oranges  contain 
nearly  the  same  pro- 
portion of  dry  matter 
as  apples,  the  larger 
part  of  which  is  sugar. 
Citric  acid  predomi- 


FIG.  13.  — GRAPHIC  COMPOSITION  OF 
ORANGE. 


FRUITS,    FLAVORS,    AND   EXTRACTS 


51 


nates  and  ranges  in  different  varieties  from  I  to  2.5  per 
cent.  The  amounts  of  protein,  fat,  and  cellulose  are 
small.  In  some  varieties  of  oranges  there  is  more  iron 
and  sulphur  than  is  usually  found  in  fruits.  All  fruits, 
however,  contain  small  amounts,  but  not  as  much  as  is 
found  in  green  vegetables.  The  average  composition 
of  oranges  is  as  follows  : 


PHYSICAL  COMPOSITION 

CHEMICAL  COMPOSITION  OF  EDI 

BLE  PORTION 

Rind 

Per  pent 

20  to  30 

Solids  

Per  Cent 

10  to  1  6 

Pulp 

.    2d  to  3d 

Sugars  

8  to  12 

Juice 

.    3d  tO   SO 

Citric  acid     .... 

.     I  to  2.d 

Ash  

o.d 

61.  Lemons  differ  from  oranges  in  containing  more 
citric  acid  and  less  sucrose,  levulose,  and  dextrose.  The 
ash  of  the  lemon  is  somewhat  similar  in  general  compo- 
sition to  the  ash  of  the  orange,  but  is  larger  in  amount. 
The  average  composition  of  the  lemon  is  as  follows : 


PHYSICAL  COMPOSITION 

CHEMICAL  COMPOSITION  OF  EDIBLE  PORTION 

Rind 

Per  Cent 
.    25  to  3d 

Per  Cent 

Solids  10  to  12 

Pulp 

.    2  d  to  3d 

Sugar  2  to  4 

Juice 

.   A.O  to  d  d 

Citric  acid     6  to  9 

62.  Grape  Fruit. — The  rind  and  seed  of  this  fruit 
make  up  about  25  per  cent,  leaving  75  per  cent  as 
edible  portion.  The  juice  contains  14  per  cent  solids,  of 


S2 


HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 


which  nearly  10  per  cent  is  sugar  and  2.5  per  cent  is 
citric  acid.  There  is  more  acid  in  grape  fruit  than  in 
oranges  and  appreciably  less  than  in  lemons.  The 
characteristic  flavor  is  due  to  a  glucoside-like  material. 
Otherwise  the  composition  and  food  value  are  about  the 
same^as  of  oranges. 

63.  Strawberries  contain  from  8  to  12  per  cent  of 
dry  matter,  mainly  sugar  and  malic  acid.  The  pro- 
tein, fat,  and  ash  usually 
make  up  less  than  2.  per 
cent.  Essential  oils  and 
coloring  substances  are 
present  in  small  amounts. 
It  has  been  estimated  that 
it  would  require  75  pounds 
of  strawberries  to  supply 
the  protein  for  a  daily  ra- 
tion. Nevertheless  they 
are  valuable  in  the  die- 
tary. It  has  been  sug- 
gested that  the  malic  and 
other  acids  have  antisep- 
tic properties  which,  add- 


FIG.  14.— GRAPHIC  COMPOSITION 
OF  STRAWBERRY. 


ed  to  the  appearance  and 
palatability,  make  them  a 
desirable  food  adjunct. 

Strawberries  have  high  dietetic  rather  than  high  food 

value. 


FRUITS,    FLAVORS,    AND   EXTRACTS  53 

64.  Grapes  contain  more  dry  matter  than  apples  or 
oranges.     There  is  no  appreciable  amount  of  protein  or 
fat,  and  while  they  add  some  nutrients,  as  sugar,  to  the 
ration,    they   do    not   contribute   any   quantity.      Their 
value,  as  in  the  case  of  other  fruits,  is  due  to  palatability 
and  indirect  effect  upon  the  digestibility  of  other  foods. 
In  the  juice  of  grapes  there  is  from  10  to  15  per  cent  or 
more  of  sugar,  as  sucrose,  levulose,  and  dextrose.    Grapes 
contain  also   from   I   to    1.5    per  cent  of   tartaric  acid, 
which,  during  the  process  of  manufacture  into  wine,  is 
rendered    insoluble   by   the    alcohol    formed,    and   the 
product,  known  as  argole,   is  used  in  the  preparation 
of   cream    of  tartar.     Differences    in    flavor   and    taste 
of   grapes   are  due    to   variations  in   the    sugar,   acid, 
and  essential  oil  content. 

65.  Peaches  contain  about  12  per  cent  of  dry  matter, 
of  which  over    10  per  cent  is  sugar  and  other  carbohy- 
drates.    There  is  less  than   1.5  percent  of  protein,  fat, 
and  mineral  matter  and  about  0.5  per  cent  of  acid.     The 
peach  contains  also  a  very  small  amount  of  hydrocyanic 
acid,  which  is  more  liberally  present  in  the  kernel  than 
in  the  fruit.     Flavor  is  imparted  mainly  by  the  sugar 
and   essential  oils.     Peaches  vary  in  composition  with 
variety  and  environment.23 

66.  Plums  contain  the  most  dry  matter  of  any  of  the 
fruits,   about  22    per   cent,  mainly  sugar.     About   one 
per  cent  is  acid  and  about  0.5  per  cent  are  protein  and 
ash.     There  are  a  great  many  varieties  of  plums,  vary- 


54        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

ing  in  composition.     Dried  plums  (prunes)  have  mildly 
laxative  properties. 

67.  Olives.  —  The  ripe   olive  contains  about   15   per 
cent  of  oil,  exclusive  of  the  pit,  which  makes  up  20  per 
cent  of  the  weight.     In  green,  preserved  olives  there  is 
considerably  less  oil.     Because  of  the  oil  the  olive  has 
food   value.     Olive  oil  is  slightly  laxative  and   assists 
mechanically  in  the  digestion  of  foods. 

68.  Figs.  —  Dried  figs  contain  about  50  per  cent  of 
sugar  and  3.5  per  cent  of  protein.     The  fig  has  a  mildly 
laxative  action. 

69.  Dried   Fruits.  —  Many   fruits    are   prepared   for 
market   by    drying.     The    dried   fruit     has    a  slightly 
different  composition   from  the  fresh  fruit   because  of 
loss  of  the  volatile  and  essential  oils,  and  minor  chemical 
changes   which  take   place  during  the  drying  process. 
When  free  from  preservatives,  dried  fruits  are  valuable 
adjuncts  to  the  dietary  and  can  be  advantageously  used 
when  fresh  fruits  are  not  obtainable. 

70.  Canning  and  Preservation  of  Fruits.  —  To  obtain 
the  best  results  in  canning,  the  fruit  should  not  be  over- 
ripe.    After  the  ripened  state  has  been  reached  fermen- 
tation and  bacterial  changes  occur,  and  it  is  more  difficult 
to  preserve  the  fruit  than  when  not  so  fully  matured.24 
When  a  fruit  has  begun  to  ferment,  it  is  hard  to  destroy 
the  ferment  bodies  and  their   spores  so  as  to  prevent 
further  ferment  action.     The  chemical  changes  that  oc- 


FRUITS,    FLAVORS,    AND    EXTRACTS  55 

cur  in  the  last  stages  of  ripening  are  similar  to  those 
which  take  place  during  the  cooking  process  whereby 
the  pectin  or  jelly-like  substances  are  rendered  more 
soluble  and  digestible. 

71.  Adulterated  Canned  Fruits.  —  Analyses  of  a  num- 
ber of  canned  fruits,  made  by  various  Boards  of  Health, 
show  the  presence  of   small   amounts   of   arsenic,  tin, 
lead,   and   other  poisonous  metals.     The  quantity  dis- 
solved depends  upon  the  kind,  age,  and  condition  of  the 
canned  goods  and  the  state  of  the  fruit  when  canned. 
The  longer  a  can  of  fruit  or  vegetable  has  been  kept  in 
stock,  the  larger  is  the  amount  of  tin  or  metal  that  has 
been  dissolved.     When  fresh  canned,  there  is  usually 
very  little  dissolved  tin,  but  in  old  goods  the  amount 
may  be  comparatively  large.     The  tin  used  for  the  can 
is  occasionally  of  poor  quality  and  may  contain  some 
arsenic,  which  also  is  dissolved.     The  occasional  use  of 
canned  goods  preserved  in  tin  is  not  objectionable,  but 
they  should  not  be  used  continually  if  it  can  be  avoided. 
Preservatives,  as  borax,  salicylic  acid,  benzoic  acid,  and 
sodium  sulphate,  are  sometimes  added  to  prevent  fer- 
mentation  and  to  preserve  the  natural  appearance  of 
the  fruit  or  vegetable.18 

72.  Fruit  Flavors  and  Extracts.  —  Formerly  all  fruit 
extracts    and    flavors    were    obtained    from    vegetable 
sources ;    at  present   many   are  made  in   the   chemical 
laboratory  by  synthetic  methods;  that  is,  by  combining 
simpler  organic  compounds  and  radicals  to  produce  the 


56        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

material  having  the  desired  flavor  and  odor.  The  vari- 
ous fruit  flavors  are  definite  chemical  compounds,  and 
can  be  produced  in  the  laboratory  as  well  as  in  the  cells 
of  plants.  When  properly  made,  there  is  no  difference 
in  chemical  composition  between  the  two.  As  prepared 
in  the  laboratory,  however,  traces  of  acids,  alkalies,  and 
other  compounds,. used  in  bringing  about  the  necessary 
chemical  combination,  are  often  present,  not  having  been 
perfectly  removed.  Hence  it  is  that  natural  and  artifi- 
cial flavors  differ  mainly  in  the  impurities  which  the 
artificial  flavors  may  contain. 

Some  of  the  flavoring  materials  have  characteristic 
medicinal  properties,  as  the  flavor  of  bitter  almond, 
which  contains  hydrocyanic  acid,  a  poisonous  substance. 
Flavors  and  extracts  should  not  be  indiscriminately  used. 
In  small  amounts  they  often  exert  a  favorable  influence 
upon  the  digestion  of  foods,  and  the  value  of  some  fruits 
is  in  a  large  measure  due  to  the  special  flavors  they  con- 
tain. A  study  of  the  separate  compounds  which  impart 
flavor  to  fruits,  as  the  various  aldehydes,  ethers,  and  or- 
ganic salts,  belongs  to  organic  chemistry  rather  than  to 
foods.  Some  of  the  simpler  compounds  of  which  flavors 
are  composed  may  exist  in  entirely  different,  form  or 
combination  in  food  products  ;  as  for  example,  pineapple 
flavoring  is  ethyl  butrate.  This  can  be  prepared  by 
combination  of  butyric  acid  from  stale  butter  with  alcohol 
which  supplies  the  ethyl  radical.  The  chemical  union 
of  the  two  produces  the  new  compound,  ethyl  butrate, 
the  distinctive  flavoring  substance  of  the  pineapple. 


FRUITS,    FLAVORS,    AND    EXTRACTS  57 

lavor  can  be  made  from  stale  butter,  caustic  soda, 
and  chloroform.  None  of  these  materials,  as  such,  go  into 
the  flavor,  but  an  essential  radical  is  taken  from  each. 
These  manufactured  products,  when  properly  made,  are 
in  every  essential  similar  to  the  flavor  made  by  the  plant 
and  stored  up  in  the  fruit.  The  plant  combines  the  ma- 
terial in  the  laboratory  of  the  plant  cell,  and  the  manu- 
facturer of  essences  puts  together  these  same  constitu- 
ents in  a  chemical  laboratory.  In  the  fruit,  however, 
the  essential  oil  is  associated  with  a  number  of  other 
compounds. 


CHAPTER   V 
SUGARS,  MOLASSES,  SYRUP,  HONEY,  AND  CONFECTIONS 

73.  Composition  of   Sugars.  —  The  term  "  sugar"   is 
applied  to  a  large  class  of  compounds  composed  of  the 
elements  carbon,  hydrogen,  and  oxygen.     Sugars  used 
for  household   purposes  are  derived  mainly  from  the 
sugar  cane  and  the  sugar  beet.25     At  the  present  time 
about  two  fifths  are  obtained  from  the  cane  and  about: 
three  fifths   from    the   beet.     When    subjected    to   the 
same  degree  of  refining,  there  is  no  difference  in  the 
chemical    composition    of   the    sugars    from    the    two 
sources;  they  are  alike  in  every  respect  and  the  chem- 
ist is  unable  to  determine  their  origin.     The  production 
of  sugar  is  an   agricultural  industry;    the  methods  of 
manufacture  pertain  more  to  industrial  chemistry  than 
to  the  chemistry  of  foods,  and  therefore  a  discussion  of 
t;hem  is  omitted  in  this  work.26 

74.  Commercial  Grades  of  Sugar.  — Sugars  are  graded 
according  to  the  size  of   the    granule,  the    color   and 
general  appearance  of  the  crystals,  and  the  per  cent 
of  sucrose  or  pure  sugar.     Common  granulated  sugar 
is  from  98.5  to  99.7  per  cent  pure  sucrose.     The  impuri- 

58 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS       59 


FIG.  15.  — SUGAR  CRYSTALS. 


ties  consist  mainly  of  moisture  and  mineral  matter. 
In  the  process  of  refining,  sulphur  fumes  are  frequently 
used  for  bleaching  and  clarifying  the  solution.26  The 
sulphurous  acid  formed 
is  neutralized  with  lime, 
which  is  rendered  insol- 
uble and  practically  all 
removed  in  subsequent 
filtrations.  There  are, 
however,  traces  of  sul- 
phates and  sulphites  in 
ordinary  sugar,  but  these 
are  in  such  small 
amounts  as  not  to  be 
injurious  to  health.  When  sugar  is  burned,  as  in  the 
bomb  calorimeter,  so  as  to  permit  collection  of  all 
of  the  products  of  combustion,  granulated  sugar  yields 
about  o.oi  of  a  per  cent  of  sulphur  dioxid.13  Occa- 
sionally coloring  substances,  as  a  small  amount  of  in- 
digo, are  added  to  yellow  tinged  sugars  to  impart 
a  white  color,  much  on  the  same  principle  as  the 
bluing  of  clothes.  The  amount  used  is  usually  ex- 
tremely small,  and  the  effect  on  health  has  never 
been  determined.  Occasionally,  however,  bluing  is 
used  to  such  an  extent  that  a  blue  scum  appears 
when  the  sugar  is  boiled  with  water.  Sugar  has  high 
value  for  the  production  of  heat  and  energy.  Diges- 
tion experiments  show  that  when  it  is  used  in  the  die- 
tary in  not  excessive  amounts,  it  is  directly  absorbed  by 


60          HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

the  body  and  practically  all  available.  It  can  advan- 
tageously be  combined  with  other  foods  to  form  a  part 
of  the  ration.27  When  a  ration  contains  the  requisite 
amount  of  protein,  sugar  is  used  to  the  best  advantage. 
Alone  it  is  incapable  of  sustaining  life,  because  it  does 
not  contain  any  nitrogen.  When  sugar  was  substituted 
for  an  excess  of  protein  in  a  ration,  it  was  found  to  pro- 
duce heat  and  energy  at  much  less  expense.  Many 
foods,  as  apples,  grapes,  and  small  fruits,  contain  appre- 
ciable amounts  of  sugar  and  owe  their  food  value  al- 
most entirely  to  their  sugar  content.  In  the  dietary, 
sugar  is  too  frequently  regarded  as  a  condiment  instead 
of  a  nutrient,  to  be  used  for  imparting  palatability 
rather  than  for  purposes  of  nutrition.  While  valuable 
for  improving  the  taste  of  foods,  the  main  worth  of 
sugar  is  as  a  nutritive  substance;  used  in  the  prepara- 
tion of  foods  it  adds  to  the  total  heat  and  energy  of  the 
ration.  Sugar  is  sometimes  used  in  excessive  amounts 
and,  as  is  the  case  with  any  food  or  nutrient,  when  that 
occurs,  nutrition  disturbances  result,  due  to  misuse  of 
the  food.  Statistics  show  that  the  average  consump- 
tion of  sugar  in  the  United  States  is  nearly  70  pounds  a 
year  per  capita.  In  the  dietary  of  the  adult,  sugar  to 
the  extent  of  four  ounces  per  day  can  be  consumed  , 
advantageously.  The  exclusion  of  sugar  from  the  diet, 
of  children  is  a  great  mistake,  as  they  need  it  for  heat 
and  energy  and  to  conserve  the  protein  for  growth. 

"  Sugar  is  one    of  the  most  important  forms  in  which   carbo- 
hydrates can  be  added  to  the  diet  of  children.     The  great  reduction 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS      6 1 

in  the  price  of  sugar  which  has  taken  place  in  recent  years  is 
probably  one  of  the  causes  of  the  improved  physique  of  the  rising 
generation.  The  fear  that  sugar  may  injure  children's  teeth  is 
largely  illusory.  The  negroes  who  live  largely  on  sugar  cane  have 
the  finest  teeth  the  world  can  show.  If  injudiciously  taken,  sugar 
may,  however,  injure  the  child's  appetite  and  digestion.  The  crav- 
ing for  sweets  which  children  show  is  no  doubt  the  natural  expres- 
sion of  a  physiological  need,  but  they  should  be  taken  with,  and  not 
between,  meals."28 

75.    Sugar  in  the  Dietary.  —  Sugar  has  an  important 
place  in  the  dietary.     It  not  only  serves  for  the  produc- 


Protea 


Fat 


FIG.  16.  — NUTRIENTS  OF  A  RATION  WITH  SUGAR. 
The  hacket  parts  represent  the  proportion  of  nutrients  not  digested. 

tion  of  heat  and  energy  in  the  body,  but  is  also  valuable 
in  enabling  the  proteids  to  be  used  more  economically. 
In  reasonable  amounts,  it  is  particularly  valuable  in  the 
dietary  of  growing  children,  as  the  proteids  of  the  food 
are  then  utilized  to  better  advantage  for  growth.  The 
unique  value  of  sugar  depends  upon  its  intelligent  use 
and  its  proper  combination  with  other  foods,  particularly 
with  those  rich  in  the  nitrogenous  compounds  or  pro- 
teids. Sugar  alone  is  incapable  of  sustaining  life,  but 
combined  with  other  foods  is  a  valuable  nutrient.  The 
amount  which  can  be  advantageously  used  depends 


62         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

largely  upon  the  individual.  Ordinarily  three  to  five 
ounces  per  day  is  sufficient,  although  some  persons  can- 
not safely  consume  as  much  as  this.  In  the  case  of 
diabetes  mellitus,  the  amount  of  sugar  in  the  ration 
must  be  materially  reduced.  Persons  in  normal  health 
and  engaged  in  outdoor  work  can  use  sugar  to  advan- 
tage.29 Many  of  the  "  harvest  drinks,  "  made  largely 
from  molasses  with  a  little  ginger,  and  used  extensively 
in  some  localities,  are  not  without  merit,  as  they  contain 


Fit 


FIG.  17.  —  NUTRIENTS  OF  A  RATION  WITHOUT  SUGAR. 
The  hacket  parts  represent  the  proportion  of  nutrients  not  digested. 

an  appreciable  amount  of  nutrients.  Milk  contains 
more  sugar  as  lactose  or  milk  sugar  than  any  other 
nutrient. 

The  craving  for  sugar  by  growing  children  and  ath- 
letes is  natural.  Sugar,  however,  is  often  injudiciously 
used,  and  a  perverted  taste  may  be  established  which 
can  be  satisfied  only  by  excessive  amounts.  This  re- 
sults in  impaired  digestion  and  malnutrition. 

76.  Maple  Sugar.  —  Sugar  obtained  by  evaporation 
from  the  sap  of  the  maple  tree  (Acer  saccharinum)  is 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS       63 

identical,  except  for  the  foreign  substances  which  it 
contains,  with  that  from  the  beet  and  sugar  cane.  The 
mottled  appearance  and  characteristic  color  and  taste  of 
maple  sugar  are  due  to  the  various  organic  acids  and 
other  compounds  present  in  the  maple  sap  and  recovered 
in  the  sugar.  Maple  sugar,  as  ordinarily  prepared,  has 
0.4  of  a  per  cent  or  more  of  ash  or  mineral  matter,  while 
refined  cane  sugar  contains  less  than  one  tenth  as  much.30 
Hence,  when  maple  sugar  is  adulterated  with  cane  and 
beet  sugars,  the  ash  content  is  noticeably  lowered,  as  is 
also  the  content  of  organic  acids.  It  is  difficult,  how- 
ever, to  determine  with  absolute  certainty  pure  high 
grade  maple  sugar  from  the  impure  low  grade  to 
which  a  small  amount  of  granulated  sugar  has  been 
added. 

77.  Adulteration  of  Sugar.  —  Sugar  at  the  present 
time  is  not  materially  adulterated.  Other  than  the 
substances  mentioned  which  are  used  for  clarification 
and  color,  none  are  added  during  refining  which  remain 
in  the  sugar  in  appreciable  amounts.  Sugar  does  not 
readily  lend  itself  to  adulteration,  as  it  has  a  definite 
crystalline  structure,  and  materials  that  would  be  suit- 
able for  its  adulteration  are  of  entirely  different  physical 
character.31  Cane  sugar  is  not  easily  blended  with 
glucose,  or  starch  sugar,  because  of  the  physical  differ- 
ences between  the  two.  The  question  of  the  kind  of 
sugar  to  use  in  the  household,  as  granulated,  loaf,  or 
pulverized,  is  largely  one  of  personal  choice,  as  there  is 


64        HUMAN    FOODS   AND   THEIR   NUTRITIVE    VALUE 

no  appreciable  difference  in  the  nutritive  value  or  purity 
of  the  different  kinds. 

78.  Dextrose  Sugars.  —  Products  known  as  glucose  and 
dextrose  sugars  are  made  from  corn  and  other  starches ; 
they  can  also  be  prepared  from  cane  sugar  by  the  use 
of  heat,  chemicals,  or  ferments  for  carrying  on  the  pro- 
cess known  as  inversion.  The  dextrose  sugars  differ 
from  cane  sugar  in  containing  a  dissimilar  number  of 
carbon,  hydrogen,  and  oxygen  atoms  in  the  molecule. 
The  formula  of  the  dextrose  sugars  is  C6H12O6,  while 
that  of  cane  sugar  is  C12H22On.  By  the  addition  of  one 
molecule  of  water,  H2O,  to  a  molecule  of  sucrose,  two 
molecules  'of  invert  sugar  (dextrose  and  glucose)  are  pro- 
duced : l  C12H22On  +  H2O  =  C6H12O6  +  C6H12O6.  In 
bringing  about  this  change,  acids  are  employed,  but  the 
acid  in  no  way  enters  into  the  chemical  composition  of 
the  final  product ;  it  is  removed  as  described  during  the 
process  of  sugar  manufacture.  The  action  of  the  acid 
brings  about  a  catalytic  change,  the  acid  being  necessary 
only  as  a  presence  reagent  to  start  the  chemical  reac- 
tion. When  properly  prepared  and  the  acid  product 
thoroughly  removed,  dextrose  and  glucose  have  practi- 
cally the  same  food  value  as  sugar.  When  they  are 
digested,  heat  and  energy  are  produced,  and  a  given 
weight  has  about  the  same  fuel  value  as  an  equal 
weight  of  sugar.  Some  of  the  glucose-yielding  products 
can  be  made  at  less  expense  than  sugar,  and  when  they 
are  sold  under  their  right  names  there  is  no  reason  why 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS       6$ 

they  should  not  be  used  in  the  dietary,  as  they  serve 
the  same  nutritive  purpose. 

79.  Molasses  is  a  by-product  obtained  in  the  refining 
of  sugar.  It  is  a  mixture  of  cane  sugar  and  invert 
sugars,  as  levulose  and  dextrose.  When  in  sugar 
making  the  sucrose  is  removed  by  crystallization,  a  point 
is  finally  reached  where  the  solution,  or  mother  liquid, 
as  it  is  called,  refuses  to  give  up  any  further  crystals ; 31 
then  this  product,  consisting  of  various  sugars  and 
small  amounts  of  organic  acids  and  ash,  is  partially  re- 
fined and  clarified  to  form  molasses.  The  term  "  New 
Orleans  "  molasses  was  formerly  applied  to  the  product 
obtained  by  the  use  of  open  kettles  for  the  manufacture 
of  sugar,  but  during  recent  years  the  vacuum  pan  pro- 
cess has  been  introduced,  and  "  New  Orleans  "  molasses 
is  now  an  entirely  different  article.  The  terms  first, 
second,  and  third  molasses  are  applied  to  the  liquids 
obtained  after  the  removal  of  the  first,  second,  and  third 
crops  of  sugar  crystals  ;  first  molasses  being  richer  in 
sucrose,  while  third  molasses  is  richer  in  dextrose  and 
invert  sugars.  The  ash  in  molasses  ranges  from  4  to 
6.5  per  cent.  Some  of  the  low  grades  of  molasses  are 
used  in  the  preparation  of  animal  foods. 

The  taste  and  physical  characteristics  of  molasses  are 
due  largely  to  the  organic  acids  and  impurities  that  are 
present,  as  well  as  to  the  proportion  in  which  the  vari- 
ous sugars  occur.  When  used  with  soda  in  cooking  and 
baking  operations,  the  organic  acid  of  the  molasses  lib- 


66        HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

crates  carbon  dioxid  gas,  which  acts  as  a  leavening 
agent.  Because  of  the  organic  acids,  molasses  should 
not  be  stored  in  tin  or  metalware  dishes,  as  the  solvent 
action  results  in  producing  poisonous  tin  and  other 
metallic  salts. 

The  food  value  of  molasses  is  dependent  entirely  upon 
the  amount  of  dry  matter  and  the  per  cent  of  sugar. 
A  large  amount  of  water  is  considered  an  adulterant ; 
ordinarily  molasses  contains  from  20  to  33  per  cent. 
If  a  sample  of  molasses  contains  75  per  cent  of  dry  mat- 
ter, it  has  slightly  less  than  three  fourths  of  the  nutritive 
value  of  the  same  weight  .of  sugar. 

80.  Syrups.  — The  term  "syrup  "  is  applied  to  natu- 
ral products  obtained  by  evaporation  and  purification  of 
the  saccharine  juices  of  plants.  Sorghum  syrup  is  from 
the  sorghum  plant,  which  is  pressed  by  machinery  and 
the  juice  clarified  and  evaporated  so  as  to  contain  about 
25  per  cent  of  water.  In  sorghum  syrups  there  are  from 
30  to  45  per  cent  of  cane  sugar,  and  from  12  to  20  per 
cent  of  glucose  and  invert  sugars.  Cane  syrup  is  made 
from  the  clarified  juice  of  the  sugar  cane,  and  has  about 
the  same  general  composition  as  sorghum  syrup.  Maple 
syrup,  prepared  from  the  juice  of  the  sugar  maple,  is 
characteristically  rich  in  sucrose  and  contains  but  little 
glucose  or  reducing  sugars.  The  flavor  of  all  the 
syrups  is  due  mainly  to  organic  acids,  ethereal  prod- 
ucts, and  impurities.  In  some  instances  the  essential 
flavor  can  be  produced  synthetically,  or  derived  from 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS       67 


other  and  cheaper  materials  ;  and  by  the  use  of  these 
flavors,  mixed  syrups  can  be  prepared  closely  resem- 
bling many  of  the  natural  products.  When  properly 
made,  they  are  equal  in  nutritive  value  to  natural  syr- 
ups. When  sold  under  assumed  names,  they  are  to  be 
considered  and  classified  as 
adulterated,  and  not  as  syr- 
ups from  definite  and  spe- 
cific products.  Low-grade 
syrups  and  molasses  are 
often  used  for  making  fuel 
alcohol.  They  readily  un- 
dergo alcoholic  fermentation 
and  are  valuable  for  this 
purpose,  rendering  it  pos- 
sible for  a  good  grade  of 
fuel  alcohol  to  be  produced 
at  low  cost.  The  manufac- 
ture of  sugar,  syrups,  and 
molasses  has  been  brought 
to  a  high  degree  of  perfec- 
tion through  the  assistance 
rendered  by  industrial  chemistry.  Losses  in  the  proc- 
ess are  reduced  to  a  minimum,  and  the  various  steps 
are  all  controlled  by  chemical  analysis.  Sugar  has 
the  physical  property  of  deflecting  a  ray  of  polar- 
ized light,  the  amount  of  deflection  depending  upon 
the  quantity  of  sugar  in  solution.  This  is  measured 
by  the  polariscope,  an  instrument  by  means  of  which 


FIG.  18.  — GRAPHIC  COMPOSITION 
OF  SYRUP. 


68         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

the    sugar   content   of   sugar    plants    is    rapidly    deter- 
mined. 

81.  Honey  is  composed  largely  of  invert  sugars  gath- 
ered by  the  honeybee  from  the  nectar  of  flowers.     It 
varies  in  composition  and  flavor  according  to  its  source. 
The  color  depends  upon  the  flower  from  which  it  came, 
white    clover   giving   a   light-colored,    pleasant-flavored 
honey,  while   that   from   buckwheat  and  goldenrod   is 
dark  and  has  a  slightly  rank  taste.     The  comb  is  com- 
posed largely  of    wax,  which  has  somewhat  the   same 
general  composition  as  fat,  but  contains  ethereal  instead 
of  glycerol  bodies.     On  account  of   the  predominance 
of  invert  sugars,  pure  honey  has  a  levulo  or  left-handed 
rotation   when    examined   by  the    polariscope.     Honey 
contains  from  60  to  75  per  cent  of  invert  sugars,  and 
from  12  to  20  per  cent  of  water,  while  the  ash  content 
is  small,  less  than  one  tenth  of  one  per  cent.     Strained 
honey   is    easily   adulterated    with    glucose    products. 
Adulteration  with    cane   sugar  is   readily  detected,  as 
pure    honey   contains   only   a    very    small    amount   of 
sucrose.       Honey    can   be   made   by   feeding   bees   on 
sugar ;    the    sugar   undergoes   inversion,  with  the  pro- 
duction of   dextrose.     Such  honey,  although  not  adul- 
terated, is   inferior   in    quality  and   lacking  in    natural 
flavor.18 

82.  Confections.  —  By    blending    various    saccharine 
products,  confections  are  made.     Usually  sucrose  (cane 
and  beet  sugar)  is  used  as  the   basis  for  their  prepa- 


SUGARS,    MOLASSES,    SYRUP,    HONEY,    CONFECTIONS       69 

ration.  Sucrose  has  definite  physical  properties,  as 
crystalline  structure,  and  forms  chemical  and  mechan- 
ical combinations  with  acid,  alkaline,  and  other  sub- 
stances ;  it  also  unites  with  water,  and  when  heated 
undergoes  changes  in  structural  composition.  The 
presence  of  small  amounts  of  acid  substances,  or  vari- 
ations in  the  concentration  of  the  sugar  solution, 
materially  affect  the  mechanical  relation  of  the  sugar 
particles  to  each  other,  and  their  crystallization.  Usu- 
ally crystallization  takes  place  when  there  is  less  than 
25  per  cent  of  water  present.  The  form,  size,  and 
arrangement  of  the  crystals  are  influenced  by  agitation 
during  cooling.  To  secure  desired  results,  often  small 
quantities  of  various  other  substances  are  employed  for 
their  mechanical  action.  Glucose  is  frequently  used, 
and  is  said  to  be  necessary  for  the  production  of  some 
•kinds  of  candy. 

Candies  are  colored  with  v,arious  dyes  and  pigments, 
many  of  which  are  harmless,  although  some  are  in- 
jurious. Coal  tar  dyes  are  frequently  employed  for 
this  purpose.  Objection  has  generally  been  urged 
against  their  use,  as  it  is  believed  many  of  them  are 
injurious  to  health.  It  cannot  be  said,  however,  that 
all  are  poisonous,  as  some  are  known  to  be  harmless. 
The  use  of  a  few  coal  tar  dyes  is  allowed  by  the  United 
States  government.  Mineral  colors  are  now  rarely, 
if  ever,  used. 

Impure  candies  result  from  objectionable  ingredients, 
as  starch,  paraffin,  and  large  amounts  of  injurious  color- 


; 


70        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

ing  substances.  Coal  tar  coloring  materials  are  identi- 
fied in  the  way  described  in  Experiment  No.  13.  Con- 
fectionery, when  properly  prepared  and  unadulterated, 
has  the  same  nutritive  value  as  sugar  and  the  other  ingre- 
dients, and  is  entitled  to  a  place  in  the  dietary  for  the 
production  of  heat  and  energy.  Much  larger  amounts 
of  candies  are  sold  and  consumed  during  the  winter 
than  the  summer  months,  suggesting  that  in  cold 
weather  candy  is  most  needed  in  the  dietary. 

83.  Saccharine  is  an  artificial  sweetening,  five  hun- 
dred times  sweeter  than  cane  sugar.  It  contains  in  its 
molecule,  chemically  united,  benzine,  sulphuric  acid,  and 
ammonia  radicals.  It  is  employed  for  sweetening  pur- 
poses in  cases  of  diabetes  mellitus,  where  physicians 
advise  against  the  use  of  sugar.  It  has  no  food  value. 
A  small  amount  is  sometimes  added  to  canned  corn 
and  tomatoes  to  impart  a  sweet  taste.  The  physio- 
logical properties  of  saccharine  have  not  been  exten- 
sively investigated. 


CHAPTER   VI 
LEGUMES  AND  NUTS 

84.  General  Composition  of  Legumes.  —  Peas,   beans, 
lentils,  and  peanuts  are  the  legumes  most  generally  used 
for  human  food.     As  a  class,  they  are  characterized  by 
high  protein  content  and  a  comparatively  low  per  cent 
of  starch  and  carbohydrates.     They  contain  the  largest 
amount  of  nitrogenous  compounds  of  any  of  the  vege- 
table foods,  and  hence  are  particularly  valuable  in  the 
human  ration  as  a  substitute  for  meats.32     For  feeding 
animals  the  legumes  are  highly  prized,  particularly  the 
forage  crops,  clover  and  alfalfa.  These  secure  their  nitro- 
gen, which  is  the  characteristic  element  of  protein,  from 
the  free  nitrogen  of  the  air,  through  the  workings  of 
bacterial  organisms  found  in  the  nodules  on  the  roots 
of  the  plants.    The  legumes  appear  to  be  the  only  plants 
capable  of  making  use  of  the  nitrogen  of  the  air  for 
food  purposes. 

85.  Beans  contain  about  24  per  cent  of  protein  and 
but  little  fat,  less  than  is  found  in  any  of  the  grain  or 
cereal  products.     The  protein  of  the  bean  differs  from 
that  of  cereals  in  its  general  and  structural  composition. 
It  is  a  globulin  known  as  legumin,  and  is  acted  upon 

71 


; 


72         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

mainly  by  ferments  working  in  alkaline  solutions,  as  in 
the  lower  part  of  the  digestive  tract.  Beans  have  about 

the  same  amount  of  ash  as  the 
cereals,  but  the  ash  is  richer  in 
potash  and  lime. 

86.   Digestibility  of  Beans. — 

Beans  are  usually  considered 
indigestible,  but  experiments 
show  they  are  quite  completely 
digested,  although  they  require 
more  work  on  the  part  of  the 
digestive  tract  than  many  other 
foods.  The  digestibility  was 
FIG.  19. -GRAPHIC  COMPOST-  found  to  vary  with  individuals, 

TION  OF  BEANS.     HACKED    86  per  cent  of  the  protein  being 

PART  INDIGESTIBLE. 

digested  in  one  case,  and  only 

72  per  cent  in  another.  The  protein  of  beans  is  not 
as  completely  digested  as  that  of  meats.  When  beans 
were  combined  with  other  foods,  forming  a  part  of 
a  ration,  they  were  more  completely  digested  than 
when  used  in  large  amounts  and  with  only  a  few  other 
foods.  The  presence  of  the  skin  is  in  part  responsible 
for  low  digestibility.  When  in  the  preparation  of  beans 
the  skins,  which  contain  a  large  amount  of  cellulose,  are 
removed,  the  beans  are  more  completely  digested.  By 
cooking  from  twenty  minutes  to  half  an  hour  in  rapidly 
boiling  water  containing  a  small  amount  of  soda,  the 
skins  are  softened  and  loosened  and  are  then  easily  re- 


LEGUMES    AND   NUTS  73 

moved  by  rubbing  in  cold  water.  Some  of  the  soda  en- 
ters into  combination  with  the  legumin.  Along  with  the 
skins  a  portion  of  the  germ  is  lost.  The  germ  readily  fer- 
ments, which  is  probably  the  cause  of  beans  producing 
flatulence  with  some  individuals  during  digestion.  After 
the  skins  are  removed  the  nutrients  are  more  susceptible 


FIG.  20.  — BEANS,  RAW  AND  COOKED.    SKINS,  WET  AND  DRY. 

to  the  action  of  the  digestive  fluids.  Experiments  show 
that  42  per  cent  of  the  protein  of  baked  skinned  beans 
is  soluble  in  pepsin  and  pancreatin  solutions,  while 
under  similar  conditions  there  is  only  3.85  per  cent  of 
the  protein  soluble  from  beans  baked  without  removal 
of  the  skins. 

87.   Use  of  Beans  in  the  Dietary.  —  There  is  no  veg- 
etable food  capable  of  furnishing  so  much  protein  at 


: 


74        HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

such  low  cost  as  beans ;  from  a  pound  costing  five  cents 
about  one  fifth  of  a  pound  of  protein  and  three  fifths  of 
a  pound  of  carbohydrates  are  obtained.  Beans  can,  to 
a  great  extent,  take  the  place  of  meats  in  the  dietary. 
There  is  more  protein  in  beans  than  in  beef.  Four 
ounces  of  uncooked  beans  or  six  ounces  of  baked  beans 
are  as  much  as  can  conveniently  be  combined  in  the 
dietary,  and  these  will  furnish  a  quarter  of  the  protein  of 
the  ration.  In  the  case  of  active  out-of-door  laborers 
over  a  pound  of  baked  beans  per  day  is  often  consumed 
with  impunity. 

88.  String  Beans.  —  String  beans  —  green  beans  with 
pod  —  contain  a  large  amount  of  water,  85  to  88  per 
cent.     The  dry  matter  is  rich  in  protein,  nearly  20  per 
cent,  although  in  the  green  beans  as  eaten,  containing 
85  per  cent  water,  there  is  less  than  2\  per  cent.     Lima 
beans  are  richer  in  protein  than  string  beans,  as  the 
green  pod  is  not  included.     String  beans  are  valuable 
both  for  the  nutrients  they  contain  and  for  the  favorable 
influence  they  exert  upon  the  digestibility  of  other  foods. 

89.  Peas.  —  In  general  composition  and  digestibility, 
peas  are  quite  similar  to  beans.     They  belong  to  the 
same  family,  Leguminosae,  and  the  protein  of  each  is 
similar  in  quantity  and  general  properties.     The  state- 
ments made  in  regard  to  the  composition,  digestibility, 
and  use  of  beans  in  the  dietary  apply  with  minor  modi- 
fications to   peas.     When    used  in   the   preparation  of 
soups,  they  add  appreciable  amounts  of  nutrients. 


LEGUMES    AND    NUTS  75 


@m 

mm 


™«tofir 


^"^ 


*/%& 


FIG.  21.  — PEA  STARCH  GRANULES. 

90.  Canned  Peas.  —  In  order  to  impart  a  rich  green 
color,  copper  sulphate  has  been  used  in  the  canning  of 
peas.  Physiologists  differ  as  to  its  effect  upon  health. 
While  a  little  may  not  be  particularly  injurious,  much 
interferes  with  normal  digestion  of  the  food  and  forms 
insoluble  copper  proteids.  In  some  countries  a  small 


76         HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

amount  of  copper  sulphate  is  tolerated,  while  in  others 
it  is  prohibited. 

91.  Peanuts.  —  Peanuts  differ  from  peas  and  beans  in 
containing  more  fat.  They  should  be  considered  a  food, 
for  at  ordinary  prices  they  furnish  a  large  amount  of 
protein  and  fat.  Like  the  other  members  of  the  legume 
family,  the  peanut  is  rather  slow  of  digestion  and  requires 
considerable  intestinal  work  for  completion  of  the  process. 

NUTS 

92.  General  Composition.  —  Nuts  should  be  regarded 
as  food,  for  they  contribute  to  a  ration  appreciable 
amounts  of  nutrients.  The  edible  portion  of  nearly  all 
is  rich  in  fat;  pecans,  for  example,  contain  as  high  as 
70  per  cent.  In  protein  content  nuts  range  from  3  per 
cent  in  cocoanuts  to  30  per  cent  in  peanuts.  The  car- 
bohydrate content  is  usually  comparatively  low,  less  than 
5  per  cent  in  hickory  nuts,  although  there  is  nearly  40 
per  cent  in  chestnuts.  On  -account  of  high  fat  content, 
nuts  supply  a  large  amount  of  heat  and  energy.33 

93.  Chestnuts  are  characterized  by  containing  less  fat 
and  protein  and  much  more  carbohydrate  material,  espe- 
cially starch,  than  is  found  in  other  nuts.  In  southern 
Europe  chestnuts  are  widely  used  as  food  ;  the  skins  are 
removed,  and  the  nuts  are  steamed,  boiled,  or  roasted, 
and  sometimes  they  are  dried  and  ground  into  flour. 
Chestnuts  are  less  concentrated  in  protein  and  fat,  and 


LEGUMES    AND    NUTS  77 

form  a  better  balanced  food  used  alone  than  do  other 
nuts. 

94.  The  Hickory  Nut,  which  is   a-  characteristically 
American  nut,  contains  in  the  edible  portion  about  15 
per  cent  protein,  65  per  cent  fat,  and  12  per  cent  car- 
bohydrates. 

95.  The   Almonds  used   in  the  United  States  come 
chiefly  from   southern  Europe,   although  they  are  suc- 
cessfully raised  in  California.     They  contain  about  55 
per  cent  fat  and   22  per  cent  protein.     The  flavor  of 
almonds  is  due  to  a  small  amount  of  hydrocyanic  acid. 

96.  Pistachio.  —  Some  nuts  are  used  for   imparting 
color  and  flavor  to  food  products,  as  the  pistachio  nut, 
the  kernel  of  which  is  greenish  in  color  and  imparts  a 
flavor  suggestive  of  almonds.     The  pistachio  has  high 
food  value,  as  it  is  rich  in  both  fat  and  protein.     It  is 
employed  in  the  manufacture  of  confectionery  and  in 
ice  cream  for  imparting  flavor  and  color. 

97.  Cocoanuts  grow  luxuriantly  in  many  tropical  coun- 
tries, and  have  a  high  food  value.     They  are  character- 
istically rich  in  fat,  one  half  of  the  edible  portion  being 
composed  of  this  nutrient.     For  tropical  countries  they 
supply  the  fat  of  a  ration  at  less  expense  than  any  other 
food.     When  used  in  large  amounts  they  should  be  sup- 
plemented with  foods  rich  in  carbohydrates,  as  rice,  and 
in  proteids,  as  beans.     Cocoanut  milk  is  proportionally 
richer  in  carbohydrates  and  poorer  in  fat  and  protein 


78         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

than  the  meat  of  the  cocoanut.     In  discussing  the  co- 
coanut,  Woods  states  : 34 

"  The  small,  green,  and  immature  nuts  are  grated  fine  for  medici- 
nal use,  and  when  mixed  with  the  oil  of  the  ripe  nut  it  be- 
comes a  healing  ointment.  The  jelly  which  lines  the  shell  of  the 
more  mature  nut  furnishes  a  delicate  and  nutritious  food.  The 
milk  in  its  center,  when  iced,  is  a  most  delicious  luxury.  Grated 
cocoanut  forms  a  part  of  the  world-renowned  East  India  condiment, 
curry.  Dried,  shredded  (desiccated)  cocoanut  is  an  important 
article  of  commerce.  From  the  oil  a  butter  is  made,  of  a  clear, 
whitish  color,  so  rich  in  fat,  that  of  water  and  foreign  substances 
combined  there  are  but  0.0068.  It  is  better  adapted  for  cooking  than 
for  table  use.  At  present  it  is  chiefly  used  in  hospitals,  but  it  is 
rapidly  finding  its  way  to  the  tables  of  the  poor,  particularly  as  a 
substitute  for  oleomargarine.1' 

98.  Use  of  Nuts  in  the  Dietary.  —  When  nuts  can  be 
secured  at  a  low  price  per  pound,  ten  cents  or  less,  they 
compare  favorably  in  nutritive  value  with  other  staple 
foods.  Digestion  experiments  with  rations  composed 
largely  of  nuts  show  that  they  are  quite  thoroughly 
digested.  Professor  Jaffa  of  the  California  Experiment 
Station,  in  discussing  the  nutritive  value  of  nuts  and 
fruits,  says :  ^ 

"  It  is  certainly  an  error  to  consider  nuts  merely  as  an  accessory 
to  an  already  heavy  meal,  and  to  regard  fruit  merely  as  something 
of  value  for  its  pleasant  flavor,  or  for  its  hygienic  or  medicinal  virtues. 
The  agreement  of  one  food  or  another  with  any  person  is  more  or 
less  a  personal  idiosyncrasy,  but  it  seems  fair  to  say  that  those  with 
whom  nuts  and  fruits  agree,  can,  if  they  desire,  readily  secure  a  con- 
siderable part  of  their  nutritive  material  from  such  sources." 


LEGUMES    AND    NUTS 


79 


AVERAGE  COMPOSITION  OF  NUTS 

(From  Fifteenth  Annual  Report,  Maine  Agricultural  Experiment  Station.) 


REFUSE 

EDIBLE 
PORTION 

EDIBLE  PORTION 

VALUE* 
PER  LB. 

Water 

Prot. 

Fat 

Carb. 

Ash 

% 

% 

% 

% 

~%~ 

% 

% 

Calories 

Almonds      .... 

64.8 

35-2 

i-7 

7-3 

19-3 

6.2 

0.7 

1065 

Almonds,  kernels 

— 

100.0 

4.8 

21.0 

549 

J7-3 

2.0 

3030 

Brazil  nuts  .... 

49.6 

50.4 

2.7 

8.6 

33-6 

3-5 

2.O 

1545 

Filberts  

52.1 

47-9 

1.8 

7-5 

3!-3 

6.2 

I.I 

1575 

Filberts,  kernels  .     . 

— 

IOO.O 

3-7 

15.6 

65-3 

13.0 

2.4 

3290 

Hickory  nuts    .     .     . 

62.2 

37-8 

1.4 

5.8 

25.5 

4-3 

0.8 

1265 

Pecans    

4Q.7 

SO.^ 

1.4 

5.2 
'* 

3^6 

7.2 

0.8 

T777 

Pecans,  kernels    .     . 

ty/ 

j^  O 

IOO.O 

•  T- 
2.9 

10.3 

jj  w 
70.8 

/ 
14-3 

i-7 

*  /  JO 

3445 

Walnuts  

;8.o 

J.2.O 

1.2 

7.O 

27.  0 

6.1 

O.7 

n8  c 

Walnuts,  kernels  .     . 

.) 

*f«>«V 

IOO.O 

2.8 

/ 
I6.7. 

**/  v 
64-4 

14.8 

/ 

i-3 

*  j^  j 
33°5 

Chestnuts    .... 

16.1 

83-9 

3I.O 

5-7 

6.7 

39-° 

i-5 

1115 

Acorns    

35-6 

64.4 

2.6 

5.2 

24.1 

30.9 

1.6 

1690 

Beechnuts   .... 

40.8 

59.2 

2.3 

13.0 

34° 

7.8 

2.1 

1820 

Butternuts  .... 

86.4 

'13.6 

0.6 

3-8 

8-3 

0.5 

0-4 

430 

Litchi  nuts  .... 

41.6 

58.4 

10.5 

i-7 

O.I 

45.2 

0.9 

875 

Pifion,  P.  edulis   .     . 

40.6 

594 

2.O 

8.7 

36.8 

IO.2 

i-7 

1905 

Pifion,  P.  monophylla 

41.7 

58.3 

2.2 

3-8 

35-4 

15-3 

1.6 

1850 

Pifion,  P.  sabiniana  . 

77.0 

23.0 

1.2 

6.5 

12.3 

1.9 

i.i 

675 

Pistachio,  kernels 

— 

IOO.O 

4.2 

22.6 

54-5 

I5.6 

3-i 

3010 

Peanuts,  raw    . 

26.4 

736 

6.9 

20.6 

30-7 

13-8 

1.6 

1935 

Peanuts,  kernels  .     . 

— 

IOO.O 

9-3 

27.9 

42.0 

I8.7 

2.1 

2640 

Roasted  peanuts  .     . 

32.6 

67.4 

i.i 

20.6 

33-i 

10.9 

i-7 

1985 

Shelled  peanuts    .     . 

— 

IOO.O 

1.6 

30-5 

49.2 

1  6.2 

2.5 

2955 

Peanut  butter  .     .     . 

— 

— 

2.0 

29-3 

46.6 

17.1 

tS-o 

2830 

Cocoanuts    .... 

48.8 

51.2 

7.2 

2.9 

25.9 

14.3 

09 

1415 

Cocoanuts,  shredded 

— 

— 

3-5 

6.3 

57-3 

31.6 

i-3 

3125 

Cocoanut  milk      .     . 

— 

•    — 

927 

0.4 

i-5 

4.6 

0.8 

97 

*  Calculated  from  analyses. 


f  Including  salt,  4. 1 . 


CHAPTER  VII 
MILK  AND  DAIRY  PRODUCTS 

99.  Importance  in  the  Dietary.  —  There  is  no  article 
of  food  which  enters  so  extensively  into  the  dietary  as 
milk,  and  it  is  one  of  the  few  foods  which  supply  all  the 
nutrients,  —  fats,  carbohydrates,  and   proteids.36     Milk 
alone  is  capable  of  sustaining  life  for  comparatively  long 
periods,  and  it  is  the  chief  article  of  food  during  many 
diseases.     An  exclusive  milk  diet  for  a  healthy  adult, 
however,  would  be  unsatisfactory ;  in  the  case  of  young 
children,  milk  is  essential,  because  the  digestive  tract 
has  not  become  functionally  developed  for  the  digestion 
of  other  foods. 

It  is  necessary  to  consider  not  only  the  composition 
and  nutritive  value  of  milk,  but  also  its  purity  or  sanitary 
condition. 

100.  General   Composition.  —  Average  milk  contains 
about  87  per  cent  water  and   13  per  cent  dry  matter. 
The  dry  matter  is  composed  approximately  of  : 


Fat 

Casein     . 
Albumin 
Milk  sugar 
Ash 


Per  Cent 
3-5 
3-25 
0.50 
5.00 
0.75 


80 


MILK   AND    DAIRY    PRODUCTS 


8l 


Fat  is  the  most  variable  constituent  of  milk.  Occa- 
sionally it  is  found  as  low  as  2  per  cent  and  as  high 
as  6  per  cent  or  more.  The  poorest  and  richest  milks 
differ  mainly  in  fat  content,  as  the  sugar,  ash,  casein, 


FIG.  22.  —  MILK  FAT  GLOBULES. 

and  albumin,  or  "  solids  of  the  milk  serum,"  are  fairly 
constant  in  amount  and  composition.  Variations  in  the 
content  of  fat  are  due  to  differences  in  feed  and  in  the 
breed  and  individuality  of  the  animal. 

101.  Digestibility.  —  Milk  is  one  of  the  most  com- 
pletely digested  of  foods,  about  95  per  cent  of  the  pro- 


82         HUMAN   FOODS    AND    THEIR    NUTRITIVE   VALUE 

tein  and  fat  and  97  per  cent  of  the  carbohydrates  being 
absorbed  and  utilized  by  the  body. 

In  a  mixed  ration,  the  nutrients  of  milk  are  practi- 
cally all  absorbed.  Milk  also  exerts  a  favorable  influ- 
ence upon  the  digestibility  of  other  foods  with  which  it 
is  combined.  This  is  doubtless  due  to  the  digestive  action 
of  the  special  ferments  or  enzymes  which  milk  contains. 
In  milk  there  is  a  soluble  ferment  material  or  enzyme 
which  has  the  power  of  peptonizing  proteids.  It  is  this 
ferment  which  carries  on  the  ripening  process  when 
cheese  is  cured  in  cold  storage,  and  it  is  believed  to  be 
this  body  which  promotes  digestion  of  other  foods  with 
which  milk  is  combined.27 

Milk  is  not  easily  digested  by  some  persons.  The 
tendency  to  costiveness  caused  by  a  milk  diet  can  be 
largely  overcome  by  the  use  of  salt  with  the  milk,  or  of 
some  solid  food,  as  toast  or  crackers,  to  prevent  coagu- 
lation and  the  formation  of  masses  resistant  to  the  di- 
gestive fluids.  Barley  water  and  lime  water  in  small 
amounts  are  also  useful  for  assisting  mechanically  in  the 
digestion  of  milk.  Milk  at  ordinary  prices  is  one  of  the 
cheapest  foods  that  can  be  used. 

102.  Sanitary  Condition  of  Milk.  —  Equally  as  im- 
portant as  composition  is  the  sanitary  condition  or 
wholesomeness  of  milk.  Milk  is  a  food  material  which 
readily  undergoes  fermentation  and  is  a  medium  for  the 
distribution  of  germ  diseases.  The  conditions  under 
which  it  is  produced  and  the  way  in  which  it  is  han- 


MILK   AND    DAIRY    PRODUCTS  83 

died  determine  largely  its  sanitary  value,  and  are  of  so 
much  importance  in  relation  to  public  health  that  during 
recent  years  city  and  state  boards  of  health  have  intro- 


FIG.  23.  — DIRT  IN  A  SAMPLE  OF  UNSANITARY  MILK. 

duced  sanitary  inspection  and  examination  of  milk  along 
with  the  chemical  tests  for  detecting  its  adulteration. 
Some  of  the  more  frequent  causes  of  contaminated  and 
unsound  milk  are:  unhealthy  animals,  poor  food  and 


84        HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 


water,  unsanitary  surroundings  of  the  animals,  and  lack 
of  cleanliness  and  care  in  the  handling  and  transporting 
of  the  milk.  Outbreaks  of  typhoid  and  scarlet  fevers 
and  other  germ  diseases  have  frequently  been  traced  to 
a  contaminated  milk  supply.37 

103.  Certified  Milk.  — When  milk  is  produced  under 
the  most  sanitary  conditions,  the  number  of   bacterial 
bodies  per  cubic  centimeter  is  materially  reduced.     In 
order  to  supply  high  grade  milk  containing  but  few  bac- 
teria, special  precautions  are  taken  in  the  care  of  the 
animals,  and  in  the  feeding  and  milking,  and  all  sources 
of  contamination  of  the  milk  are  eliminated  as  far  as  pos- 
sible.    Such    milk,  when  sold  in  sterilized   bottles,  is 
commonly   called   "certified    milk,"   indicating  that  its 
purity  is  guaranteed  by  the  producer  and  that  the  num- 
ber of  bacteria  per  unit  does  not  exceed  a  certain  stand- 
ard, as   8000   per   cubic  centimeter.     Ordinary  market 
milk  contains  upwards  of  50,  ooo. 

104.  Pasteurized    Milk.  —  In   order    to   destroy   the 
activity  of  the  bacterial  organisms,   milk   is    subjected 
to  a  temperature  of  157°  F.  for  ten  minutes  or  longer, 
which  process  is  known  as  pasteurization.     When  milk 
is  heated  to  a  temperature  above  180°,  it  is  sterilized. 
Below  157°,  the  albumin  is  not  coagulated.     By  pasteur- 
izing, milk  is  much  improved  from  a  sanitary  point  of 
view,  and  whenever   the    milk  supply  is  of    unknown 
purity,  it  should  be  pasteurized.38     After  the  milk  has 
been  thus  treated,  the  same  care  should  be  exercised  in 


MILK    AND    DAIRY    PRODUCTS 


keeping  it  protected  to  prevent  fresh  inoculation  or  con- 
tamination, as  though  it  were  unpasteurized  milk.  For 
family  use  milk  can  be  pas- 
teurized in  small  amounts  in 
the  following  way :  Before 
receiving  the  milk,  the  re- 
ceptacle should  be  thor- 
oughly cleaned  and  sterilized 
with  boiling  water  or  dry 
heat,  as  in  an  oven.  The 
milk  is  loosely  covered  and 
placed  in  a  pan  of  water,  a 

false    bottom    being    in    the 

FIG.  24.  — PASTEURIZING  MILK. 
pan  so  as  to  prevent  unequal 

heating.  The  water  surrounding  the  milk  is  gradually 
heated  until  a  temperature  of  159°  F.  is  registered,  and 
the  milk  is  kept  at  this  temperature  for  about  ten 
minutes.  It  is  then  cooled  and  placed  in  the  refrigerator. 

105.  Tyrotoxicon. — Tyrotoxicon  is  a  chemical  com- 
pound produced  by  a  ferment  body  which  finds  its  way 
into  milk  when  kept  in  unsanitary  surroundings.  It 
induces  digestion  disorders  similar  to  cholera,  and  when 
present  in  large  amounts,  may  prove  fatal.  It  some- 
times develops  in  cream,  ice  cream,  or  cheese,  but  only 
when  they  have  been  kept  in  unclean  places  or  pro- 
duced from  infected  milk. 

601.  Color  of  Milk  is  often  taken  as  a  guide  to  its 
purity  and  richness  in  fat.  While  a  yellow  tinge  is 


86        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

usually  characteristic  of  milks  rich  in  fat,  it  is  not  a 
hard  and  fast  rule,  for  frequently  light-colored  milks 
are  richer  in  fat  than  yellow-tinged  ones.  The  coloring 
material  is  independent  of  the  percentage  of  fat,  and  it 
is  not  always  safe  to  judge  the  richness  of  milk  on  the 
basis  of  color. 

107.  Souring  of  Milk.  —  Souring  of  milk  is  due  to  the 
action  of  the  lactic  acid  organism,  which  finds  its  way 
into  the  milk  through  particles  of  dust  carried  in  the 
air  or  from  unclean  receptacles  which  contain  the  spores 
of  the  organism.39     When  milk  sours,  a  small  amount  of 
sugar  is  changed  to  lactic  acid  which  reacts  upon  the 
casein,  converting  it  from  a  soluble  to  an  insoluble  con- 
dition.    When  milk  is  exposed  to  the  air  at  a  temperature 
of  from  70°  to  90°  F.,  lactic  acid  fermentation  readily  takes 
place.     At  a  low  temperature  the  process  is  checked, 
and  at  a  high  temperature  the  organisms  and  spores  are 
destroyed.     In  addition  to  lactic  acid  ferments,  there  are 
large  numbers  of  others  which  develop  in  milk,  chang- 
ing the  different  compounds  of  which  milk  is  composed. 
In  the  processes  of  butter  and  cheese  making,  these 
fermentation  changes  are  controlled  so  as  to  develop 
the  flavor  and  secure   the  best  grades  of   butter  and 
cheese. 

108.  Use   of   Preservatives   in   Milk.  —  In   order    to 
check  fermentation,  boric  acid,  formalin,  and  other  pre- 
servatives have  been  proposed.     Physiologists  object  to 
their  use  because  the  quantity  required  to  prevent  fer- 


MILK   AND    DAIRY    PRODUCTS  87 

mentation  is  often  sufficient  to  have  a  medicinal  effect. 
The  tendency  is  to  use  excessive  amounts,  which  may 
interfere  with  normal  digestion  of  the  food.  Milk  that 
is  cared  for  under  the  most  sanitary  conditions  has  a 
higher  dietetic  value  and  is  much  to  be  preferred  to  that 
which  has  been  kept  sweet  by  the  use  of  preservatives. 

109.  Condensed  Milk  is  prepared  by  evaporating  milk 
in  vacuum  pans  until  it  is  reduced  about  one  fourth  in 
bulk,  when  it  is  sealed  in  cans,  and  it  will  then  keep 
sweet  for  a  long  time.     Occasionally  some  cane  sugar 
is   added   to   the   evaporated   product.     When   diluted, 
evaporated  milk  has  much   the    same   composition    as 
whole  milk.     When  a  can  of  condensed  milk  has  been 
opened,  the  same  care  should  be  exercised  to  prevent 
fermentation  as  if  it  were  fresh  milk. 

110.  Skim  Milk  differs   in    composition  from  whole 
milk  in  fat  content.     When  the  fat  is  removed  by  the 
separator,  there  is  often  left  less  than  one  tenth  of  a 
per  cent.     Skim  milk  has  a  much  higher  nutritive  value 
than  is  generally  conceded,  and  wherever  it  can  be  pro- 
cured at  a  reasonable  price  it  should  be  used  in  the 
dietary  as  a  source  of  protein. 

111.  Cream  ranges  in  fat  content  from   15  to  35  per 
cent.     It  is  generally  preferred  to  whole  milk,  although 
it  is  not  as  well  balanced  a  food,  because  it  is  deficient 
in  protein.     Cream  should  contain  at  least  25  per  cent 
of  fat. 


88         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

112.  Buttermilk  is  the  product  left  after  removal  of 
the  fat  from  cream  by  churning.     It  has  about  the  same 
amount  of  nutrients  as  skim  milk.     The  casein  is  in  a 
slightly  modified  form  due  to  the  development  of  lactic 
acid   during  the  ripening   of   the  cream,   and  on   this 
account  buttermilk  is  more  easily  digested  and  assimi- 
lated by  many  individuals  than  milk  in   other  forms. 
The   development   of   the   acid   generally  reduces  the 
number  of  species  of  other  than  the  lactic  organisms, 
and  these  are  increased. 

113.  Goat's  Milk  is  somewhat  richer  in  solids  than 
cow's  milk,  containing  about  one  per  cent  more  proteids, 
a  little  more  fat,  and  less  sugar.     When  used  as  a  sub- 
stitute for  human  or  cow's  milk,  it  generally  needs  to  be 
slightly  diluted,  depending,  however,  upon  the  composi- 
tion of  the  individual  sample. 

114.  Koumiss  is  a  fermented  beverage   made   from 
milk  by  the  use  of  yeast  to  secure  alcoholic  fermenta- 
tion.    Koumiss  contains  about  one    per  cent  each  of 
lactic  acid  and  alcohol,  and  the  casein  and  other  nutri- 
ents are  somewhat  modified  by  the  fermentation  changes. 
Koumiss  is  generally  considered  a  non-alcoholic  beverage 
possessing  both  food  and  dietetic  value. 

115.  Prepared  Milks. — Various  preparations  are  made 
to   resemble   milk  in  general   composition.     These  are 
mechanical  mixtures  of  sugar,  fats,  and  proteids.     Milk 
sugar,   casein,    or    malted    proteids   are   generally  the 


MILK    AND    DAIRY    PRODUCTS  89 

materials  employed  in  their  preparation.  Often  the 
dried  and  pulverized  solids  of  skim  milk  are  used. 
Many  of  the  prepared  milks  are  deficient  in  fat.  While 
they  are  not  equal  to  cow's  milk,  their  use  is  often  made 
necessary  from  force  of  circumstances. 

116.  Human  Milk  is  not  as  rich  in   solid  matter   as 
cow's  milk.     It  contains  about  the  same  amount  of  fat, 
one  per  cent  more  sugar,  and  one  per  cent  less  proteids. 
In  human  milk  nearly  one  half  of  the  protein  is  in  the 
form  of  albumins,  while  in  cow's  milk  there  is  about  one 
fifth  in  this  form.     The  fat  globules  are  much  smaller 
than  those  of  cow's  milk.     In  infant  feeding  it  is  often 
necessary   to    modify    cow's    milk    by   the   addition   of 
water,  cream,  and  milk  sugar,  so  as  to  make  it  more 
nearly  resemble  in  composition  human  milk. 

117.  Adulteration  of  Milk.  —  Milk  is   not  as   exten- 
sively adulterated  as  it  was  before  the  passage  and  en- 
forcement of   the    numerous   state  and  municipal  laws 
regulating  its  inspection  and  sale.     The  most  frequent 
forms  of  adulteration  are  addition  of  water  and  removal 
of  cream.     These  are  readily  detected  from  the  specific 
gravity   and   fat   content   of   the   milk.      The   specific 
gravity  of  milk  is  determined  by  means  of  the  lactom- 
eter, an  instrument  which  sinks  to  a  definite  point  in 
pure  milk.     In  watered  milk  it  sinks  to  greater  depth, 
depending  upon  the  amount  of  water  added.     The  fat 
content  of  milk  is  readily  and  accurately  determined  by 
the  Babcock  test,  in  which  the  fat  is  separated  by  cen- 


#«u  -- 


\   / 


FIG.  25.  — APPARATUS  USED  IN  TESTING  MILK. 

i,  pipette  ;    2,  lactometer  ;    3,  acid  measure  ;    4,  centrifuge  ; 
5,  test  bottle. 

90 


MILK   AND    DAIRY    PRODUCTS  9! 

trifugal  action.  For  the  detection  of  adulterated  milk 
the  student  is  referred  to  Chapter  VI,  "  Chemistry  of 
Dairying,"  by  Snyder. 

BUTTER 

118.  Composition.  —  Butter  is  made  by  the  churning 
or  agitation  of  cream  and  is  composed  mainly  of  milk 
fats  and  water,  together  with  smaller  amounts  of  ash, 
salt,  casein,  milk  sugar,  and  lactic  acid.  Average 
butter  has  the  following  composition : 


Water  . 
Ash  and  salt 
Casein  and  albumin 
Fat 


Per  Cent 
10.5 

2.5 

1.0 

86.0 


When  butter  contains  an  abnormal  amount  of  water, 
it  is  considered  adulterated.  According  to  act  of  Con- 
gress standard  butter  should  not  contain  over  16  per 
cent  of  water  nor  less  than  82.5  per  cent  of  fat. 

119.  Digestibility  of  Butter.  —  Digestion  experiments 
show  that  practically  all  of  the  fat,  98  per  cent,  is  di- 
gestible and  available  for  use  by  the  body.  Butter  is 
valuable  only  for  the  production  of  heat  and  energy. 
Alone,  it  is  incapable  of  sustaining  life,  because  it  con- 
tains no  proteid  material.  It  is  usually  one  of  the  more 
expensive  items  of  food,  but  it  is  generally  considered 
quite  necessary  in  a  ration.5  It  has  been  suggested 


. 


92         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

that  it   takes  an    important   part   mechanically  in    the 
digestion  of  food. 

120.  Adulteration  of  Butter.  —  In  addition  to  contain- 
ing an  excess  of   water,  butter  is  adulterated  in  other 
ways.     Old,  stale  butter  is  occasionally  melted,  washed, 
salted,  and  reworked.     This  product  is  known  as  reno- 
vated butter,  and  has  poor  keeping  qualities.    Frequently 
preservatives  are  added  to  such  butter  to  delay  fermen- 
tation changes.     Oleomargarine  and  butterine  are  made 
by  mixing  vegetable  and  animal  fats.40     Highly  colored 
stearin,  cotton-seed  oil,  and  lard  are  the  usual  materials 
from  which  oleomargarine  is  made.     It  has  practically 
the  same  composition,  digestibility,  and  food  value  as 
butter.     When  sold  under   its   true    name    and  not   as 
butter,  there  is  no  objection,  as  it  is  a  valuable  food  and 
supplies  heat  and  energy  at  less  cost  than  butter.     The 
main  objection  to  oleomargarine  and  butterine  is  that 
they  are  sold  as  butter.41 

The  coloring  of  butter  is  not  generally  looked  upon 
as  adulteration,  for  butter  naturally  has  a  more  or 
less  yellow  tinge.  According  to  an  act  of  Congress, 
butter  colors  of  a  non-injurious  character  are  allowed 
to  be  used. 

CHEESE 

• 

121.  General  Composition.  —  Cheese  is  made  by  the 

addition  of  rennet  to  ripened  milk,  resulting  in  coagu- 
lation of  the  casein,  which  mechanically  combines  with 


MILK    AND    DAIRY    PRODUCTS  93 

the  fat.  It  differs  from  butter  hv  composition  by  con- 
taining, in  addition  to  fat,  casein  and  appreciable 
amounts  of  mineral  matter.  The  composition  varies 
with  the  character  of  the  milk  from  which  the  cheese 
was  made.  Average  milk  produces  cheese  containing 
a  larger  amount  of  fat  than  proteids,  while  cheese  from 
skimmed  or  partially  skimmed  milk  is  proportionally 
poorer  in  fat.  Ordinarily  there  is  about  35  per  cent  of 
water,  33  per  cent  of  fat,  and  27  per  cent  of  casein,  and 
albumin  or  milk  proteids,  the  remainder  being  ash,  salt, 
milk  sugar,  and  lactic  acid.  Cheese  is  characterized  by 
its  large  percentage  of  both  fat  and  protein,  and  has 
high  food  value.  It  contains  more  fat  and  protein  than 
any  of  the  meats ;  in  fact,  there  are  but  few  foods  which 
have  such  liberal  amounts  of  these  nutrients  as  cheese. 

The  odor  and  flavor  of  cheese  are  due  to  workings  of 
bacteria  which  result  in  the  production  of  aromatic  com- 
pounds. The  purity  and  condition  of  the  milk,  as  well 
as  the  method  of  manufacture  and  the  kind  of  ferment 
material  used,  determine  largely  the  flavor  and  odor. 
Cheese  is  generally  allowed  to  undergo  a  ripening  or 
curing  process  before  it  is  used  as  food.  The  changes 
resulting  consist  mainly  in  increased  solubility  of  the 
proteids,  with  the  formation  of  a  small  amount  of  amid 
and  aromatic  compounds.42 

122.  Digestibility.  —  Cheese  is  popularly  considered  an 
indigestible  food,  but  extended  experiments  show  that 
it  is  quite  completely  digested,  although  in  the  case  of 


94  HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

some  individuals  not  easily  digested.     In  general,  about 

95  per  cent  of  the  fat  and  92  per  cent  and  more  of  the 
protein  is  digested,  depending  upon  the  general  com- 
position of  the  cheese  and  the  digestive  capacity  of  the 
individual.     As  far  as  total  digestibility  is  concerned, 
there  appears  to  be  but  little  difference  between  green 
and  well-cured  cheese.     So  far  as  ease  of  digestion  is 
concerned,  it  is  probable  that  some  difference   exists. 
There  is  also  but  little  difference  in  digestibility  result- 
ing from  the  way  in  which  milk  is  made  into  cheese,  the 
nutrients  of  Roquefort,  Swiss,  Camembert,  and  Cheddar 
being  about  equally  digestible.13    The  differences  in  odor 
and  taste  are  due  to  variations  in  kind  and  amount  of 
bacterial  action.     When    combined   with    other   foods, 
cheese  may  exercise  a  beneficial  influence  upon  diges- 
tion in  the  same  way  as  noted  from  the  use  of  several 
foods  in  a  ration.     No  material  differences   were   ob- 
served in  digestibility  when  cheese  was  used  in  small 
amounts,  as  for  condimental  purposes,  or  when  used  in 
large  amounts  to  furnish  nutrients.     Artificial  digestion 
experiments  show  that  cheese  is  more  readily  acted  upon 
by  the  pancreatic  than  by  the  gastric  fluids,  suggest- 
ing that  cheese  undergoes  intestinal  rather  than  gastric 
digestion.     It  is  possible  this  is  the  reason  that  cheese 
is  slow  of  digestion  in  the  case  of  some  individuals. 

123.  Use  in  the  Dietary.  —  Cheese  should  be  used  in 
the  dietary  regularly  and  in  reasonable  amounts,  rather 
than  irregularly  and  then  in  large  amounts.  Cheese  is 


MILK    AND    DAIRY    PRODUCTS  95 

not  a  luxury,  but  ordinarily  it  is  one  of  the  cheapest  and 
most  nutritious  of  human  foods.  A  pound  of  cheese 
costing  15  cents  contains  about  a  quarter  of  a  pound  of 
protein  and  a  third  of  a  pound  of  fat ;  at  the  same  price, 
beef  yields  only  about  half  as  much  fat  and  less  protein. 
Cheese  at  18  cents  per  pound  furnishes  more  available 
nutrients  and  energy  than  beef  at  12  cents  per  pound. 
In  the  dietary  of  European  armies,  cheese  to  a  great 
extent  takes  the  place  of  beef.  See  Chapter  XVI. 

124.  Cottage  Cheese  is  made  by  coagulating  milk  and 
preparing  the  curd  by  mixing  with  it  cream  or  melted 
butter  and  salt  or  sugar  as  desired.     When  milk  can  be 
procured   at   little   cost,  cottage   cheese   is  one  of  the 
cheapest  and  most  valuable  foods.43 

125.  Different  Kinds  of  Cheese.  —  By  the  use  of  dif- 
ferent kinds  of  ferments  and  variations  in  the  process 
of  manufacture  different  types  or  kinds  of  cheese  are 
made,  as  Roquefort,  Swiss,  Edam,  Stilton,  Camembert, 
etc.     In  the  manufacture  of  Roquefort  cheese,  which  is 
made  from  goats'  and  ewes'  milk,  bread  is  added  and 
the  cheese  is  cured  in  caves,  resulting  in  the  formation 
of  a  green  mold  which  penetrates  the  cheese  mass,  and 
produces  characteristic  odor  and  flavor.     Stilton  is  an 
English  soft,  rich  cheese  of  mild  flavor,  made  from  milk 
to  which  cream  is  usually  added.     It  is  allowed  to  un- 
dergo an  extended  process  of  ripening,  often  resulting 
in  the   formation  of  bluish   green   threads    of    fungus. 
Limburger  owes  its  characteristic  odor  and  flavor  to  the 


96        HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


action  of  special  ferment  bodies  which  carry  on  the 
ripening  process.  Neufchatel  is  a  soft  cheese  made 
from  sweet  milk  to  which  the  rennet  is  added  at  a  high 
temperature.  After  pressing,  it  is  kneaded  and  worked, 
and  then  put  into  packages  and  covered  with  tin  foil. 

126.  Adulteration    of    Cheese.  —  The    most   common 
forms  of  adulteration  are  the  manufacture  of  skim-milk 
cheese  by  the  removal  of  the  fat  from  the  milk,  and 
substitution  of  cheaper  and  foreign  fats,  making  a  prod- 
uct known  as  filled  cheese.     When  not  labeled  whole 
milk  cheese,  or  sold  as  such,  there  is  no  objection  to 
skim-milk  cheese.     It  has  a  high  food  value  and  is  often 
a  cheap  source  of  protein.     The  manufacture  of  filled 
cheese  is  now  regulated  by  the  national  government, 
and  all  such  cheese  must  pay  a  special  tax  and  be  prop- 
erly labeled.     As  a  result,  the  amount  of  filled  cheese 
upon  the  market  has  very  greatly  decreased,  and  cheese 
is  now  less  adulterated  than  in  former  years.     The  na- 
tional dairy  law  allows  the  use  of  coloring  matter  of  a 
harmless  nature  in  the  manufacture  of  cheese. 

127.  Dairy  Products  in  the  Dietary. — The  nutrients 
in  milk  are  produced  at  less  expense  for  grain  and  for- 
age than  the  nutrients  in  beef,  hence  from  a  pecuniary 
point  of  view,  dairy  products,  as  milk  and  cheese,  have 
the  advantage.     In  the  case  of  butter,  however,  the  cost 
usually  exceeds  that  of  meat.     In  older  agricultural  re- 
gions, where  the  cost  of  beef  production  reaches  the 


MILK    AND    DAIRY    PRODUCTS  97 

maximum,  dairying  is  generally  resorted  to,  as  it  yields 
larger  financial  returns,  and  as  a  result  more  cheese  and 
less  beef  are  used  in  the  dietary.  As  the  cost  of  meats 
is  enhanced,  dairy  products,  as  cheese,  naturally  take 
their  place. 


CHAPTER   VIII 
MEATS   AND  ANIMAL  FOOD  PRODUCTS 

128.  General  Composition.  — Animal  tissue  is  composed 
of  the  same  classes  of  compounds  as  plant  tissue.  In 
each,  water  makes  up  a  large  portion  of  the  weight, 
and  the  dry  matter  is  composed  of  nitrogenous  and  non- 
nitrogenous  compounds,  and  ash  or  mineral  matter. 
Plants  and  animals  differ  in  composition  not  so  much  as 
to  the  kinds  of  compounds,  although  there  are  differences, 
but  more  in  the  percentage  amounts  of  these  compounds. 
In  plants,  with  the  exception  of  the  legumes,  the  protein 
rarely  exceeds  14  per  cent,  and  in  many  vegetable  foods, 
when  prepared  for  the  table,  there  is  less  than  2  per 
cent.  In  meats  the  protein  ranges  from  15  to  20  per 
cent.  The  non-nitrogenous  compounds  of  plants  are 
present  mainly  in  the  form  of  starch,  sugar,  and  cellulose, 
while  in  animal  bodies  there  are  only  traces  of  carbohy- 
drates, but  large  amounts  of  fat.  Fat  is  the  chief  non- 
nitrogenous  compound  of  meats ;  it  ranges  between 
quite  wide  limits,  depending  upon  kind,  age,  and  general 
condition  of  the  animal.  Meats  contain  the  same  gen- 
eral classes  of  proteins  as  the  vegetable  foods ;  in  each 
the  proteins  are  made  up  of  albumins,  glubulins,  albu- 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  99 

minates,  peptone-like  bodies,  and  insoluble  proteids. 
The  larger  portion  of  the  protein  of  meats  and  cereals 
is  in  insoluble  forms.  The  meat  juices,  which  contain 
the  soluble  portion  of  the  proteins,  constitute  less  than 
5  per  cent  of  the  nitrogenous  compounds.  Meats  con- 
tain less  amid  substances  than  plants,  in  which  the  amids 


FIG.  26.  — MEAT  AND  EXTRACTIVE  SUBSTANCES. 

are  produced  from  ammonium  compounds  and  are  sup- 
posed to  be  intermediate  products  in  the  formation  of 
proteids,  while  in  the  animal  body  they  are  derived  from 
the  proteids  supplied  in  the  food  and,  it  is  generally  be- 
lieved, cannot  form  proteids.  Albuminoids  make  up 
the  connective  tissue,  hair,  and  skin,  and  are  more  abun- 
dant in  animal  than  in  plant  tissue.  One  of  the  chief 
albuminoids  is  gelatine.  Both  plant  and  animal  foods 


100       HUMAN    FOODS   AND    THEIR    NUTRITIVE    VALUE 

undergo  bacterial  changes  resulting  in  the  production  of 
alkaloidal  bodies  known  as  ptomaines,  of  which  there 
are  a  large  number.  These  are  poisonous  and  are  what 
cause  putrid  and  stale  meat  to  be  unwholesome.  The 
protein  in  meat  differs  little  in  general  composition  from 
that  of  vegetable  origin";  differences  in  structure  and 
cleavage  products  between  the  two  are,  however,  notice- 
able. 

While  meats  from  different  kinds  of  animals  have 
somewhat  the  same  general  composition,  they  differ  in 
physical  properties,  and  also  in  the  nature  of  the  various 
nutrients.  For  example,  pork  contains  less  protein  than 
beef,  but  the  protein  of  pork  is  materially  different  from 
that  of  beef,  as  a  larger  portion  is  in  the  form  of  soluble 
proteids,  while  in  beef  more  is  present  in  an  insoluble 
form.  Not  only  are  differences  in  the  percentage  of 
individual  proteins  noticeable,  but  there  are  equally  as 
great  differences  in  the  fats.  As  for  example :  some  of 
the  meats  have  a  larger  proportion  of  the  fat  as  stearin 
than  do  others.  Hence  meats  differ  in  texture  and  taste 
more  than  in  nutritive  value,  due  to  the  variations  in  the 
percentage  of  the  different  proteins,  fats,  and  extractive 
material,  rather  than  to  differences  in  the  total  amounts 
of  these  compounds.  The  taste  and  flavor  of  meat  is  to 
a  large  extent  influenced  by  the  amount  of  extractive 
material. 

While  the  nutrients  of  meats  are  divided  into  classes, 
as  proteins  and  fats,  there  are  a  large  number  of  sepa- 
rate compounds  which  make  up  each  of  the  individual 


MEATS    AND    ANIMAL    FOOD    PRODUCTS 


101 


classes,  and  there  are  also  small  amounts  of  compounds 
which  are  not  included  in  these  groups. 

129.   Beef.  —  About  one  half  of  the  weight  of  beef  is 
water ;   the  lean  meat  contains  a  much  larger  amount 


FIG.  27.  —  STANDARD  CUTS  OF  BEEF. 
(From  Office  of  Experiment  Station  Bulletin.) 

than  the  fat.  As  a  rule,  the  parts  of  the  animal  that 
contain  the  most  fat  contain  the  least  water.  In  some 
meats  there  is  considerable  refuse,  25  to  30  per  cent. 
In  average  meat  about  12  per  cent  of  the  butcher's 
weight  is  refuse  and  non-edible  parts.44  A  pound  of 
average  butcher's  meat  is  about  one  half  water,  and  over 


UNIV.  or 


102        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

10  per  cent  waste  and  refuse,  which  leaves  less  than 
40  per  cent  fat  and  protein.  Meat  is  generally  con- 
sidered to  have  a  high  nutritive  value,  due  to  the  com- 
paratively large  amounts  of  fat  and  protein.  Beef 
contains  more  protein  than  any  vegetable  food,  except 
the  legumes,  and  from  i  to  1.5  per  cent  mineral  matter, 
exclusive  of  bone.  Some  of  the  mineral  matter  is  chemi- 
cally united  with  the  protein  and  other  compounds. 
While  figures  are  given  for  average  composition  of  beef, 
it  is  to  be  noted  that  wide  variations  are  frequently  to 
be  met  with,  some  samples  containing  a  much  larger 
amount  of  waste  and  trimmings  than  others,  and  this 
influences  the  per  cent  of  the  nutritive  substances.  In 
making  calculations  of  nutrients  consumed,  as  in  dietary 
studies,  the  figures  for  average  composition  of  meat 
should  be  used  only  in  cases  where  the  samples  do  not 
contain  an  excess  either  of  fat  or  trimmings.45  When 
very  lean,  there  is  often  a  large  amount  of  refuse,  and 
the  meat  contains  less  dry  matter  and  is  of  poorer  flavor 
than  from  animals  in  prime  condition.  In  the  case  of 
very  fat  animals,  a  large  amount  of  waste  results,  and 
the  flavor  is  sometimes  impaired. 

130.  Veal  differs  from  beef  in  containing  a  smaller 
amount  of  dry  matter,  richer  in  protein,  but  poorer  in  fat. 
Animals  differ  in  composition  at  different  stages  of 
growth  in  much  the  same  way  as  plants.  In  the  earlier 
stages  protein  predominates  in  the  plant  tissue,  while 
later  the  carbohydrates  are  added  in  larger  amounts, 


MEATS    AND    ANIMAL    FOOD    PRODUCTS 


reducing  the  percentage  content  of  protein.  In  animals 
the  same  is  noticeable.  Young  animals  are,  pound  for 
pound,  richer  in  protein  than  old  animals.  While  in  the 
case  of  vegetables  the  increase  in  size,  or  rotundity,  is 
due  to  starch  and  carbohydrates,  in  animals  it  is  due  to 
the  addition  of  fat.  But  plants,  like  animals,  observe 
the  same  general  laws  as  to  changes  in  composition  at 
different  stages  of  growth. 


FIG.  28.  — STANDARD  CUTS  OF  MUTTON. 
(From  Office  of  Experiment  Station  Bulletin.) 

131.  Mutton.  —  There  is  about  the  same  amount  of 
refuse  matter  in  mutton  as  in  beef.  In  a  side  of  mutton 
about  19  per  cent  are  trimmings  and  waste,  and  in  a 
side  of  beef  18.5  per  cent.  Mutton,  as  a  rule,  contains 
a  little  more  fat  and  dry  matter  than  beef,  and  some- 
what less  protein.  A  side  of  beef,  as  purchased,  con- 


104       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

tains  about  50  per  cent  of  water,  14.5  per  cent  protein, 
and  16.8  per  cent  of  fat,  while  a  side  of  mutton,  as  pur- 
chased, contains  42.9  per  cent  water,  12.5  per  cent 
protein,  and  24.7  per  cent  fat.  A  pound  of  beef  yields 
a  smaller  number  of  calories  by  25  per  cent  than  a 
pound  of  mutton.  At  the  same  price  per  pound  more 
nutrients  can  be  purchased  as  mutton  than  as  beef. 
The  differences  in  composition  between  lamb  and 
mutton  are  similar  to  those  between  veal  and  beef  ;  viz. 
a  larger  amount  of  water  and  protein  and  a  smaller 
amount  of  fat  in  the  same  weight  of  the  young  animals. 
Differences  in  composition  between  the  various  cuts  of 
lamb  are  noticeable.  The  leg  contains  the  least  fat 
and  the  most  protein,  while  the  chuck  is  richest  in  fat 
and  poorest  in  protein.  As  in  the  case  of  beef,  many 
of  the  cheaper  cuts  contain  as  much  or  more  nutrients 
than  the  more  expensive  cuts.  They  are  not,  however, 
as  palatable  and  differ  as  to  toughness  and  other  physi- 
cal characteristics. 

132.  Pork  is  characterized  by  a  high  per  cent  of  fat 
and  a  comparatively  low  per  cent  of  protein.  It  is  gen- 
erally richest  in  fat  of  any  of  the  meats.  The  per  cent 
of  water  varies  with  the  fatness  of  the  animal ;  in  very 
fat  animals  there  is  a  smaller  amount,  while  lean  ani- 
mals contain  more.  In  lean  salt  pork  there  is  about  20 
per  cent  water,  and  in  fat  salt  pork  about  7  per  cent. 
There  is  less  refuse  and  waste  in  pork  than  in  either 
beef  or  mutton.  Ham  contains  from  14  to  15  per  cent 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  105 

of  refuse,  and  bacon  about  7  per  cent.  Bacon  has 
nearly  twice  as  much  fat  and  a  smaller  amount  of  pro- 
tein than  ham.  A  pound  of  bacon,  as  purchased,  will 
yield  nearly  twice  as  much  energy  or  fuel  value  as  a 
pound  of  ham.  Digestion  experiments  show  that  bacon 
is  quite  readily  and  completely  digested  and  is  often  a 


FIG.  29.  — STANDARD  CUTS  OF  PORK. 
(From  Office  of  Experiment  Station  Bulletin.) 

cheaper  source  of  fat  and  protein  than  other  meats. 
There  is  about  three  times  as  much  fat  in  bacon  as  in 
beef.  When  prepared  for  the  table  bacon  contains 
from  40  to  50  per  cent  of  fat.  A  pound  of  high  grade, 
lean  bacon  furnishes  from  o.i  to  0.3  of  a  pound  of  digest- 
ible protein  and  from  0.4  to  0.6  of  a  pound  of  digestible 
fat,  which  is  about  two  thirds  as  much  fat  as  is  found 
in  butter.  Bacon  contains  nearly  as  much  digestible 


106       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

protein  as  other  meats  and  from  two  to  three  times  as 
much  fat,  making  it,  at  the  same  price  per  pound,  a 
cheaper  food  than  other  meats.  In  salt  pork  there  is 
from  60  to  85  per  cent  of  fat,  and  less  protein  than  in 
bacon.  The  protein  and  fat  of  pork  differ  from  those 
in  beef  not  only  in  percentage  amounts,  but  also  in  the 
nature  of  the  individual  proteins  and  fats.  The  com- 
position of  pork  varies  with  the  nature  of  the  food  that 
is  consumed  by  the  animal.  Experiments  show  that 
it  is  possible  by  judicious  feeding  in  the  early  stages  of 
growth  to  produce  pork  with  the  maximum  of  lean 
meat  and  the  minimum  of  fat.  After  the  animal  has 
passed  a  certain  period,  it  is  not  possible  by  feeding  to 
materially  influence  the  percentage  of  nutrients  in  the- 
meat.  The  flavor,  too,  of  pork,  as  of  other  meats,  is 
dependent  largely  upon  the  nature  of  the  food  the 
animal  consumes.  When  there  is  a  scant  amount  of 
available  protein  in  the  ration,  the  meat  is  dry,  nearly 
tasteless,  and  contains  less  of  the  soluble  nitrogenous 
compounds  which  impart  flavor  and  individuality. 

133.  Lard  is  prepared  from  the  fat  of  swine,  and  is 
separated  from  associated  tissue  by  the  action  of  heat. 
A  large  amount  of  fat  is  found  lining  the  back  of 
the  abdominal  cavity,  and  this  is  known  as  leaf  lard. 
Slight  differences  are  noticeable  in  the  composition  and 
quality  of  lard  made  from  different  parts  of  the  hog. 
Leaf  lard  is  usually  considered  the  best.  Lard  is  com- 
posed of  the  three  fats,  olein,  stearin,  and  palmatin,  and 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  107 

has  a  number  of  characteristic  physical  properties,  as 
specific  gravity,  melting  point,  iodine  absorption  num- 
ber, as  well  as  behavior  with  various  reagents,  and 
these  enable  the  mixing  of  other  fats  with  lard  to  be 
readily  detected.  Lard  is  used  in  the  preparation  of 
oleomargarine,  and  it  is  also  combined  with  various 
vegetable  oils,  as  cotton-seed  oil,  in  the  making  of  imita- 
tion or  compound  lards.46  Lard  substitutes  differ  little 
in  general  composition  from  pure  lard,  except  in  the 
structure  of  the  crystals  and  the  percentage  of  the  vari- 
ous individual  fats. 

134.  Texture  and  Toughness  of  Meats.  —  In  discuss- 
^ing  the  texture  of  meats,  Professor  Woods  states  : 45 

"  Whether  meats  are  tough  or  tender  depends  upon  two  things : 
the  character  of  the  walls  of  the  muscle  tubes  and  the  character  of 
the  connective  tissues  which  bind  the  tubes  and  muscles  together. 
In  young  and  well-nourished  animals  the  tube  walls  are  thin  and 
delicate,  and  the  connective  tissue  is  small  in  amount.  As  the  ani- 
mals grow  older  or  are  made  to  work  (and  this  is  particularly  true 
in  the  case  of  poorly  ^nourished  animals),  the  walls  of  the  muscle 
tubes  and  the  connective  tissues  become  thick  and  hard.  This  is 
the  reason  why  the  flesh  of  young,  well-fed  animals  is  tender  and 
easily  masticated,  while  the  flesh  of  old,  hard-worked,  or  poorly  fed 
animals  is  often  so  tough  that  prolonged  boiling  or  roasting  seems 
to  have  but  little  effect  on  it. 

"  After  slaughtering,  meats  undergo  marked  changes  in  texture. 
These  changes  can  be  grouped  under  three  classes  or  stages.  In 
the  first  stage,  when  the  meat  is  just  slaughtered,  the  flesh  is  soft, 
juicy,  and  quite  tender.  In  the  next  stage  the  flesh  stiffens  and  the 
meat  becomes  hard  and  tough.  This  condition  is  known  as  rigor 
mortis,  and  continues  until  the  third  stage,  when  the  first  changes  of 


108       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

decomposition  set  in.  In  hot  climates  the  meat  is  commonly  eaten 
in  either  the  first  or  second  stage.  In  cold  climates  it  is  seldom 
eaten  before  the  second  stage,  and  generally,  in  order  to  lessen  the 
toughness,  it  is  allowed  to  enter  the  third  stage,  when  it  becomes 
soft  and  tender,  and  acquires  added  flavor.  The  softening  is  due  in 
part  to  the  formation  of  lactic  acid,  which  acts  upon  the  connective 
tissue.  The  same  effect  may  be  produced,  though  more  rapidly,  by 
macerating  the  meat  with  weak  vinegar.  Meat  is  sometimes  made 
tender  by  cutting  the  flesh  into  thin  slices  and  pounding  it  across 
the  cut  ends  until  the  fibers  are  broken." 

135.   Influence   of   Cooking  upon  the  Composition   of 

Meats.47  —  It  is  believed  by  many  that  losses  are  pre- 
vented and  the  nutritive  value  conserved  when,  in  the 
cooking  of  meat,  it  is  placed  directly  into  boiling  water 
rather  than  into  cold  water  and  then  brought  to  the 
boiling  point  and  cooked. )  Extensive  experiments  have 
been  made  by  Dr.  Grindley  in  regard  to  this  and  other 
points  connected  with  the  cooking  of  meats,  and  in  gen- 
eral it  was  found  that  the  temperature  of  the  water  in 
which  the  meat  was  placed  made  little  difference  in 
its  nutritive  value  or  the  amount  of  material  extracted. 
It  was  found  that  by  both  methods  there  was  dissolved 
2.3  per  cent  of  the  protein  matter,  i  per  cent  of  the 
nitrogenous  extractives,  1.6  per  cent  of  non-nitrogenous 
material,  and  0.8  per  cent  of  ash,  of  the  raw  meat,  which 
was  equivalent  to  about  13  per  cent  of  the  total  proteid 
material  and  81  per  cent  of  the  ash.  The  cold  water 
extract  contained  bodies  coagulated  by  heat.  Cold 
water  did  not  extract  any  of  the  fat,  but  during  the  pro- 
cess of  cooking,  appreciable  amounts  were  lost  mechani- 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  IOQ 

cally.  Cooked  meats  were  found  to  be  less  soluble  in 
cold  water  than  raw  meats.  During  the  process  of 
boiling,  meat  shrinks  in  weight  about  40  or  45  per  cent, 
depending  mainly  upon  the  size  of  the  pieces  and  the 
content  of  fat.  The  loss  in  weight  is  practically  a  loss 
of  water,  and  the  loss  of  nutrients,  all  told,  amounts  to 
about  4  per  cent,  or  more,  depending  upon  the  mechan- 
ical loss.48  But  slight  differences  were  found  in  the 
composition  of  the  meats  cooked  three  and  five  hour 
periods. 

"  Careful  study  in  this  laboratory  has  shown  that  when  meat  is 
cooked  in  water  at  80°  to  85°  G.,  placing  meat  in  hot  or  cold  water 
at  the  start  has  little  effect  on  the  amount  of  nutrients  in  the  meat 
which  passes  into  the  broth.  The  meat  was  in  the  form  of  cubes,  one 
to  two  inches,  and  in  pieces  weighing  from  one  to  two  pounds. 

"  It  is  commonly  supposed  that  when  meat  is  plunged  into  boiling 
water,  the  albumin  coagulates  and  forms  a  crust,  which  prevents  the 
escape  of  nutritive  materials  into  the  broth.  It  is  also  believed  that 
if  a  rich  broth  is  desired,  to  be  used  either  as  a  soup  or  with  the  meat 
as  a  stew,  it  is  more  desirable  to  place  the  meat  in  cold  water  at  the 
start.  From  the  results  of  these  experiments,  however,  it  is  evident 
that,  under  these  conditions,  there  can  be  little  advantage  in  using 
hot  or  cold  water  at  the  beginning.  When  meats  were  cooked  by 
dry  heat,  as  in  roasting,  a  larger  amount  of  nutrients  was  rendered 
soluble  in  water  than  during  boiling.  The  losses  of  nutrients  were 
much  smaller  when  meats  were  cooked  by  dry  heat  than  when  cooked 
in  water,  being  on  the  average,  water  3 5  per  cent,  nitrogenous  extrac- 
tives 9  per  cent,  non-nitrogenous  extractives  17  per  cent,  fat  7  per 
cent,  ash  12  per  cent,  and  a  small  loss  of  protein.'' 

The  nutrients  in  the  broth  of  the  meat  started  in 
hot  water  amounted  to  about  i  per  cent  of  protein, 


110       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

I  per  cent  of  fat,  and  0.5  per  cent  of  ash,  the  amount  of 
nutrients  being  directly  proportional  to  the  length  of 
time  and  temperature  of  the  cooking.  In  general,  the 
larger  the  pieces,  the  smaller  the  losses.  Beef  that  has 
been  used  in  the  preparation  of  beef  tea  loses  its  extrac- 
tive materials,  which  impart  taste  and  flavor,  but  there 
is  only  a  small  loss  of  actual  nutritive  value.  Clear 
meat  broth  contains  little  nutriment  —  less  than  unfiltered 
broth.  Most  of  the  nitrogenous  material  of  the  broth  is 
in  the  form  of  creatin,  sarkin,  and  xanthin,  nitrogenous 
extractives  or  amid  substances  having  a  much  lower 
food  value  than  proteids.  Experiments  show  that  some 
of  these  extractives  have  physiological  properties  slightly 
stimulating  in  their  action,  and  it  is  believed  the  stimulat- 
ing effect  of  a  meat  diet  is  in  part  due  to  these.49  They 
are  valuable  principally  for  imparting  taste  and  flavor, 
and  cannot  be  regarded  as  nutrients.  The  variations  in 
taste  and  flavor  of  meats  from  different  sources  are  due 
largely  to  differences  in  extractive  material. 

"  In  general,  the  various  methods  of  cooking  materially  modify  the 
appearance,  texture,  and  flavor  of  meat,  and  hence  its  palatability,  but 
have  little  effect  on  total  nutritive  value.  Whether  it  be  cooked  in 
hot  water,  as  in  boiling  or  stewing,  or  by  dry  heat,  as  in  roasting, 
broiling,  or  frying,  meat  of  all  kinds  has  a  high  food  value,  when 
judged  by  the  kind  and  amount  of  nutrient  ingredients  which  are 
present."  50 

Beef  extracts  of  commerce  contain  about  50  per  cent  of 
extractive  matters,  as  amids,  together  with  smaller 
amounts  of  soluble  proteids  ;  ash,  mainly  added  salt,  is 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  III 

also  present  in  liberal  amounts  (20  per  cent).  Beef 
extracts  have  condimental  value  imparting  taste  and 
flavor,  which  make  them  useful  for  soup  stocks,  but 
they  furnish  little  in  the  way  of  nutritive  substance. 

136.  Miscellaneous  Meat  Products.  —  By  combining 
different  parts  of  the  same  animal,  or  different  meats,  a 
large  number  of  products  known  as  sausage  are  made. 
These  vary  in  composition  with  the  ingredients  used. 
In  general,  they  are  richer  in  fat  than  beef  and  contain 
about  the  same  amount  of  protein.  Potato  flour  and 
flour  from  cereals  are  sometimes  used  in  their  prepara- 
tions, but  the  presence  of  any  material  amount,  unless 
so  stated  on  the  package,  is  considered  an  adulter- 
ant. 

Pickled  meats  are  prepared  by  the  use  of  condiments, 
as  salt,  sugar,  vinegar,  and  saltpeter.  During  the  smok- 
ing and  curing  of  meats,  no  appreciable  losses  of  nutri- 
ents occur.51  The  smoke  acts  as  a  preservative,  and 
imparts  condimental  properties.  Saltpeter  (potassium 
nitrate)  has  been  used  from  earliest  times  in  the  prepa- 
ration of  meats  ;  it  preserves  color  and  delays  fermenta- 
tion changes.  When  used  in  moderate  amounts  it 
cannot  be  regarded  ^as  a  preservative  or  injurious  to 
health.  Excessive  amounts,  however,  are  objectionable. 
Smoked  meats,  prepared  with  or  without  saltpeter,  give 
appreciable  reactions  for  nitrites,  compounds  formed 
during  combustion  of  the  wood  by  which  the  meat  was 
smoked.  Many  vegetables  contain  naturally  much 


112         HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

larger  amounts  of  nitrates,  taken  from  the  soil  as  food, 
than  meat  that  has  been  preserved  with  saltpeter.52 

137.  Poultry.  —  The  refuse  and  waste  from  chickens, 
as  purchased  on  the  market,  ranges  from   15  to  30  per 
cent.     The  fat  content  is  much  lower  than  in  turkeys  or 
ducks,  the  largest  amount  being  found  in  geese.     The 
edible  portion  of  all  fowls  is  rich  in  protein,  particularly 
the  dark  meat,  and  the  food  value  is  about  equal  to  that 
of  meat  in  general.     When  it  is  desired  to  secure  a  large 
amount  of  protein  with  but  little  fat,  chicken  supplies 
this,  perhaps,  better  than  any   other  animal  food.     A 
difference  is  observed  in  the  composition  of  the  meat  of 
young  and  old  fowls  similar  to  that  between  beef  and 
veal.     The  physical  composition  and,  to  a  slight  extent, 
the  solubility  of  the  proteids  are  altered  by  prolonged 
cold  storage,  the  difference  being  noticeable  mainly  in  the 
appearance  of  the  connective  tissue  of  the  muscles.     In 
discussing  poultry  as  food,  Langworthy  states  :  53 

"A  good,  fresh  bird  shows  a  well-rounded  form,  with  neat,  compact 
legs,  and  no  sharp,  bony  angles  on  the  breast,  indicating  a  lack  of 
tender  white  meat.  The  skin  should  be  a  clear  color  (yellow  being 
preferred  in  the  American  market)  and  free  from  Blotches  and  pin 
feathers ;  if  it  looks  tight  and  drawn,  the  bird  has  probably  been 
scalded  before  being  plucked.  The  flesh  should  be  neither  flabby 
nor  stiff,  but  should  give  evenly  and  gently  when  pressed  by  the 
finger." 

138.  Fish.  —  From  30  to  60  per  cent  of  the  weight 
of  fresh  fish   is   refuse.     The   edible   portion   contains 


MEATS    AND   ANIMAL    FOOD    PRODUCTS  113 

from  35  to  50  per  cent,  and  in  some  cases  more,  of 
water.  The  dry  matter  is  rich  in  protein ;  richer  than 
many  meats.  The  nutrients  in  fish  range  between 
comparatively  wide  limits,  the  protein  in  some  cases 
being  as  low  as  6  per  cent,  in  flounder,  and  in  others 
as  high  as  30  per  cent,  in  dried  codfish.  The  amount 
of  fat,  except  in  a  few  cases,  as  salmon  and  trout, 
is  small.  Salmon  is  the  richest  in  fat  of  any  of  the 
fishes.  When  salted  and  preserved,  the  proportion  of 
water  is  lessened  and  that  of  the  nutrients  is  increased. 
Fish  can  take  the  place  of  meat  in  the  dietary,  but 
it  is  necessary  to  add  a  larger  amount  of  fat  to  the  ra- 
tion because  of  the  deficiency  of  most  fish  in  this  ingre- 
dient. Fish  has  about  the  same  digestibility  as  meats. 
It  is  believed  by  many  to  be  valuable  because  it  supplies 
a  large  amount  of  available  phosphates.  Analyses, 
however,  show  that  the  flesh  of  fish  contains  no  more 
phosphorus  compounds  than  meats  in  general,  and  its 
food  value  is  due  to  protein  rather  than  to  phosphates.54 
Fish  appears  to  be  as  completely  and  easily  digested 
as  meats.  Differences  in  flavor,  taste,  and  palatability  are 
due  to  small  amounts  of  flavors  and  extractive  materials, 
varying  according  to  the  food  consumed  by  the  fish 
and  the  conditions  under  which  they  lived.  The  flesh 
of  fish  decays  more  readily  than  that  of  other  meats 
and  produces  ptomaines,  or  toxic  substances,  which  are 
the  result  of  fermentation  changes  usually  associated 
with  putrefaction.  Cases  of  poisoning  from  eating  un- 
sound fish  are  not  infrequent.55 


114        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

Shellfish  have  about  the  same  general  composition  as 
fish.  In  clams  there  is  a  larger  amount  of  dry  matter 
than  in  oysters,  which  contain  about  12  per  cent,  half 
of  which  is  protein.  When  placed  in  fresh  water,  the 
oyster  increases  in  size  and  undergoes  the  process 
known  as  "fattening."  Oftentimes  impure  water  is 
used  for  this  purpose,  which  makes  the  eating  of  raw 
oysters  a  questionable  practice  from  a  sanitary  point: 
of  view,  as  the  water  in  which  they  are  floated  often 
contains  disease-producing  germs,  as  typhoid.  During 
the  process  of  fattening,  although  the  oyster  increases 
in  size  and  weight,  it  decreases  in  percentage  of  nutri- 
ents. In  discussing  the  composition  of  oysters, 
Atwater  states  : 7 

"  They  come  nearer  to  milk  than  almost  any  other  food  material 
as  regards  both  the  amounts  and  relative  proportions  of  nutrients.11 

139.  Eggs,  General  Composition.  —  Eggs  are  a  type 
of  concentrated  nitrogenous  food.  About  75  per  cent 
(shell  removed)  is  water,  about  one  third  is  yolk,  and 
a  little  over  50  per  cent  is  albumin  or  white.  The 
shell  makes  up  from  10  to  12  per  cent  of  the  weight. 
The  yolk  and  white  differ  widely  in  composition. 
The  yolk  contains  a  much  larger  per  cent  of  solids  than 
the  white,  and  is  rich  in  both  fat  and  protein,  from  a 
third  to  a  half  of  the  weight  being  fat.  The  white  has 
about  the  same  amount  of  water,  88  per  cent,  as  aver- 
age milk,  but,  unlike  milk,  the  dry  matter  is  mainly 
albumin.  The  entire  egg  (edible  portion)  contains  about 


MEATS    AND    ANIMAL    FOOD    PRODUCTS 


equal  parts  of  fat  and  protein;  12  to  13  per  cent  of 
each  and  an  appreciably  large  amount  of  ash  or  mineral 
matter,  —  from  0.8  to  i  per 
cent,  consisting  mainly  of 
phosphates  associated  with 
the  albumin.  There  is  no 
material  difference  in  chem- 
ical composition  between 
white  and  dark  shelled  eggs, 
or  between  eggs  with  differ- 
ent colored  yolks.  It  is 
simply  a  question  of  color- 
ing matter.  The  egg  is  in- 
fluenced to  an  appreciable 
extent  by  feed  and  general 
care  of  the  fowls.  The 
egg  and  the  potato  contain 
about  the  same  amount  of 
water.  They  are,  however,  distinct  types  of  food, 
the  potato  being  largely  composed  of  carbohydrates 
and  the  egg  of  protein  and  fat.  Eggs  resemble  meat 
somewhat  in  general  composition,  although  they  con- 
tain rather  less  of  protein  and  fat.  When  eggs  are 
boiled  there  is  a  loss  of  weight  due  to  elimination  of 
water;  otherwise  the  composition  is  unaltered,  the 
coagulation  of  the  albumin,  as  stated  in  Chapter  I, 
consisting  simply  in  a  rearrangement  of  the  atoms  of 
the  molecule.  The  egg  is  particularly  valuable  in  the 
dietary  of  the  convalescent,  when  it  is  desired  to  secure 


FIG.  30.  —  GRAPHIC  COMPOSITIQN 
OF  AN  EGG. 


Il6        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

the  maximum  amount  of  phosphorus  in  organic  combi- 
nation. 

The  flavor  of  eggs  is  in  part  due  to  the  food  supplied 
to  the  fowls,  as  well  as  the  age  of  the  egg.  Experi- 
ments show  that  onions  and  some  other  vegetables, 
when  fed  to  fowls,  impart  odors  and  taste  to  the  eggs. 
The  keeping  qualities  of  eggs  are  also  dependent  upon 
the  food  supplied.  In  experiments  at  the  Cornell  Ex- 
periment Station,  when  hens  were  fed  on  a  narrow, 
nitrogenous  ration,  a  large  number  of  eggs  were  pro- 
duced containing  the  minimum  amount  of  solid  matter 
i^and  of  poor  keeping  quality,  while  a  larger  sized  egg  of 
better  keeping  quality  was  obtained  when  a  variety  of 
foods,  nitrogenous  and  non-nitrogenous,  was  supplied. 

140.  Digestibility  of  Eggs.  —  Digestion  experiments 
show  that  there  is  but  little  difference  in  the  digestibil- 
ity of  eggs  cooked  in  different  ways.  A  noticeable  dif- 
ference, however,  is  observed  in  the  rapidity  with  which 
the  albumin  and  proteids  are  dissolved  in  a  pepsin  solu- 
tion. In  general,  it  was  found  that,  when  the  albumin 
was  coagulated  at  a  temperature  of  180°,  it  was  more 
rapidly  and  completely  dissolved  in  the  pepsin  than 
when  coagulated  at  a  temperature  of  212°.  When  eggs 
were  cooked  at  a  temperature  of  212°,  the  hard-boiled 
eggs  appeared  to  be  slightly  more  digestible  than  the 
soft-boiled  eggs,  but  the  digestion  was  not  as  complete 
as  when  the  cooking  was  done  at  a  temperature  of  180° ; 
then  no  difference  in  digestibility  was  found  between 


MEATS    AND    ANIMAL    FOOD    PRODUCTS  117 

eggs  cooked  for  a  short  or  a  long  time.  The  egg  is 
one  of  the  most  completely  digested  of  all  foods, 
practically  all  the  protein  and  fat  being  absorbed  and 
available  to  the  body.  Langworthy,  in  discussing  Joris- 
senne's  investigations  on  .  the  digestibility  of  eggs, 
states  :  ^ 

"  The  yolk  of  raw,  soft-boiled,  and  hard-boiled  eggs  is  equally 
digestible.  The  white  of  soft-boiled  eggs,  being  semi-liquid,  offers 
little  more  resistance  to  the  digestive  juices  than  raw  white.  The 
white  of  a  hard-boiled  egg  is  not  generally  very  thoroughly  masti- 
cated. Unless  finely  divided,  it  offers  more  resistance  to  the  diges- 
tive juices  than  the  fluid  or  semi-fluid  white,  and  undigested  particles 
may  remain  in  the  digestive  tract  many  days  and  decompose.  From 
this  deduction  it  is  obvious  that  thorough  mastication  is  a  matter  of 
importance.  Provided  mastication  is  thorough,  marked  differences 
in  the  completeness  of  digestion  of  the  three  sorts  of  eggs,  in  the 
opinion  of  the  writer  cited,  will  not  be  found." 

141.  Use  of  Eggs  in  the  Dietary.  —  When  eggs  are  at 
the  same  price  per  dozen  as  meat  is  per  pound,  they 
furnish  a  larger  amount  of  nutrients.  In  general,  a 
dozen  eggs  have  a  little  higher  food  value  than  a  pound 
of  meat.  Eggs  are  usually  a  cheaper  source  of  food 
because  a  smaller  amount  is  served  than  of  meat. 
When  eggs  are  25  cents  per  dozen,  the  cost  of  ten  eggs 
for  a  family  of  five  is  less  than  that  of  a  pound  or  a 
pound  and  a  quarter  of  beef  at  22  cents  per  pound. 
The  meat,  however,  would  furnish  the  larger  amount  of 
nutrients.  Eggs  are  valuable,  too,  in  the  dietary  be- 
cause they  are  frequently  combined  with  flour,  cereal 


Il8         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

products,  and  vegetables,  which  contain  a  large  amount 
of  starch,  and  some  of  which  contain  small  amounts  of 
protein.  This  combination  furnishes  a  balanced  ration, 
as  well  as  secures  palatability  and  good  mechanical 
combination  of  the  foods.  Eggs  in  combination  with 
flour,  sugar,  butter,  and  other  materials  have  equally 
as  great  a  value  as  when  used  alone  and  as  a  substitute 
for  meat. 

Eggs  vary  in  weight  from  17.5  to  28  ounces,  and 
more  per  dozen.  They  should  be  purchased  and  sold  by 
weight.  -When  stored,  eggs  lose  weight.  The  egg  can- 
not be  considered  as  entirely  germ  proof,  and  care  is 
necessary  in  its  handling  and  use,  the  same  as  with 
other  food  articles.  The  cause  of  the  spoiling  of  eggs 
is  due  largely  to  exterior  bacterial  infection. 

CANNED  MEATS 

142.  General  Composition.  —  Canned  meats  differ  but 
little  in  composition  from  fresh  meats.  Usually  during 
the  process  of  cooking  and  canning  there  is  a  slight 
increase  in  the  amount  of  dry  matter,  but  the  relative 
proportion  of  protein  and  fat  is  about  the  same  as  in 
fresh  meat.  It  is  frequently  stated  that  the  less  salable 
parts  are  used  in  the  preparation  of  canned  meats,  as 
it  is  possible  by  cooking  and  the  addition  of  condiments 
to  conceal  the  inferior  physical  properties.  As  to  the 
accuracy  of  these  statements,  the  author  is  unable  to 
say.  The  shrinkage  or  loss  in  weight  during  canning 


MEATS   AND   ANIMAL   FOOD    PRODUCTS  1 19 

amounts  to  from  30  to  40  per  cent.  The  liquids  in 
which  the  cooking  and  parboiling  are  done  are  some- 
times used  in  the  preparation  of  beef  extracts.  Salt, 
saltpeter,  and  condiments  are  generally  added  during 
the  canning  process.  Saltpeter  is  used,  as  it  assists  in 
retaining  the  natural  color  and  prevents  some  objection- 
able fermentation  changes.  In  moderate  amounts  it 
is  not  generally  considered  an  adulterant.  An  exten- 
sive examination  by  Wiley  and  Bigelow  of  packing- 
house products  and  preserved  meats  showed  that  of 
the  latter  only  a  small  amount  contained  objectionable 
preservatives.  The  authors,  after  an  extended  inves- 
tigation, reported  favorably  upon  their  composition  and 
sanitary  value,  saying  they  found  "  so  little  to  criti- 
cise and  so  much  to  commend  in  these  necessary  prod- 
ucts." In  this  bulletin  they  do  not  classify  saltpeter 
as  an  adulterant.51 

Where  fresh  meats  cannot  be  secured,  canned  meats 
are  often  indispensable.  Usually  the  nutrients  of 
canned  meats  cost  more  than  those  of  fresh  meats, 
and  in  their  use  as  food  much  care  should  be  ex- 
ercised to  prevent  contamination  after  opening  the 
cans.  Occasionally  the  meat  contains  ferment  mate- 
rials that  have  not  been  entirely  destroyed  during 
cooking,  and  these,  when  the  cans  are  stored  in  warm 
places,  develop  and  cause  deleterious  changes  to 
occur.  Consequently  canned  meats  should  be  stored 
at  a  low  temperature.  By  recent  congressional  act, 
these  preparations  are  now  made  under  the  super- 


120         HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

vision  of  government  inspectors.  All  diseased  animals 
are  rejected,  and  the  sanitary  conditions  under  which 
the  meat  is  prepared  have  been  greatly  improved. 
Formerly,  the  most  frequent  forms  of  adulteration 
were  substitution  of  one  meat  for  another,  as  the 
mixing  of  veal  with  chicken,  and  the  use  of  preserva- 
tives, as  borax  and  sulphites.  While  the  cost  of  the 
nutrients  in  canned  meats  is  generally  much  higher 
than  in  fresh  meats,  the  latter  ar-e  not  always  easily 
obtained,  or  capable  of  being  kept  for  any  length  of 
time,  and  hence  canned  meats  are  often  indispensable. 


CHAPTER   IX 
CEREALS 

143.  Preparation  and  Cost  of  Cereals. — The  grains 
used  in  the  preparation  of  cereal  foods  are  wheat,  oats, 
corn,  rice,  and,  to  a  less  extent,  barley  and  rye.  For 
some  of  these  the  entire  cleaned  grain  is  ground  or 
pulverized,  while  for  others  the  bran  and  germ  are  first 
removed.  In  order  to  improve  their  keeping  qualities, 
they  are  often  sterilized  before  being  put  up  in  sealed 
packages.  Special  treatment,  as  steaming  or  malting, 
is  sometimes  given  to  impart  palatability  and  to  lessen 
the  time  required  for  cooking.  As  a  class,  the  cereal 
foods  are  clean,  nutritious,  and  free  from  adulteration. 
Extravagant  claims  are  sometimes  made  as  to  their 
food  value,  and  frequently  excessive  prices  are  charged, 
out  of  proportion  to  the  cost  of  the  nutrients  in  the  raw 
material.  Within  recent  years  the  number  of  cereal 
preparations  has  greatly  increased,  due  to  improve- 
ments and  variations  in  the  methods  of  manufacture.56 

Cereal  foods  are  less  expensive  than  meats  and  the 
various  animal  food  products.  They  contain  no  refuse, 
are  easily  prepared  for  the  table,  and  may  be  kept 
without  appreciable  deterioration.  Some  of  the  ready- 


: 


122        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

to-eat  brands  are  cooked,  dried,  and  crushed,  and  sugar, 
glucose,  salt,  and  various  condimental  materials  added 
to  impart  taste.  Others  contain  malt,  or  are  subjected 
to  a  malting  or  germinating  process  to  develop  the 
soluble  carbohydrates,  and  such  foods  are  sometimes 
called  predigested.  It  is  believed  that  the  cereals  are 
being  more  extensively  used  in  the  dietary,  which  is 
desirable  both  from  an  economic  and  a  nutritive  point 
of  view.  Special  care  is  necessary  in  the  cooking  and 
preparation  of  cereals  for  the  table,  in  order  to  develop 
flavor  and  bring  about  hydration  and  rupturing  of  the 
tissues,  as  explained  in  Chapter  II. 

144.  Corn  Preparations.  —  Corn  or  maize  is  character- 
ized by  a  high  per  cent  of  fat  and  starch,  and,  compared 
with  wheat  and  oats,  a  low  content  of  protein.57  Re- 
moval of  the  bran  and  germ  lessens  the  per  cent  of  fat. 
The  germ  is  removed  principally  because  it  imparts 
poor  keeping  qualities.  Many  of  the  corn  breakfast 
foods  contain  i  per  cent  or  less  of  fat  and  from  8  to  9 
per  cent  of  protein.  Coarsely  ground  corn  foods  are 
not  as  completely  digested  and  assimilated  as  those 
more  finely  ground.  As  in  the  case  of  wheat  products, 
the  presence  of  the  bran  and  germ  appears  to  prevent 
the  more  complete  absorption  of  the  nutrients.  Finely 
ground  corn  meal  compares  favorably  in  digestibility 
with  wheat  flour.  Corn  flour  is  prepared  by  removal 
of  the  bran  and  germ  and  granulation  of  the  more 
starchy  portions  of  the  kernel,  and  has  better  keeping 


CEREALS  123 

qualities  than  corn  meal  from  which  the  bran  and  germ 
have  not  been  so  completely  removed.  At  times  corn 
flour  has  been  sufficiently  low  in  price  to  permit  its  use 
for  the  adulteration  of  wheat  flour.  The  mixing  of  corn 
and  wheat  flours,  however,  is  prohibited  by  law  unless 


FIG.  31.  — CORN  STARCH. 

the  product  is  so  labeled.  When  combined  with  wheat 
flour,  corn  bread  and  various  other  articles  of  food  are 
prepared,  but  used  alone  corn  flour  is  not  suitable  for 
bread  making,  because  its  gluten  lacks  the  binding 
properties  imparted  to  wheat  flour  by  the  gliadin.  It 
is  essential  that  corn  be  used  with  foods  of  high  protein 
content  so  as  to  make  a  balanced  ration  ;  for  when  it 
forms  a  large  part  of  the  dietary,  the  ration  is  apt  to  be 


124      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

deficient  in  protein.  In  a  mixed  dietary,  corn  is  one  of 
the  cheapest  and  best  cereals  that  can  be  used.  Too 
frequently,  however,  excessive  prices  are  charged  for 
corn  preparations  that  contain  no  more  nutrients  than 
ordinary  corn  meal.  There  is  no  difference  between 
yellow  and  white  corn  meal  so  far  as  nutritive  value  is 
concerned. 

145.  Oat  Preparations  are  characterized  by  large 
amounts  of  both  protein  and  fat.  Because  of  the 
removal  of  the  hulls,  they  contain  more  protein  than 
the  original  grain.  The  oat  preparations  differ  little  in 
chemical  composition.  They  all  have  about  16  per  cent 
of  protein,  7  per  cent  of  fat,  and  65  per  cent  of  starch, 
and  are  richer  in  ash  or  mineral  matter  than  other 
cereals.  The  main  difference  is  in  method  of  prepara- 
tion and  mechanical  composition.  Some  are  partially 
cooked  and  then  dried.  Those  costing  7  cents  or  more 
per  pound  do  not  contain  any  greater  amount  of  nutri- 
tive substance  than  those  purchased  in  bulk  at  about 
half  the  price.  At  one  time  it  was  believed  that  oats 
contained  a  special  alkaloid  having  a  stimulating  effect 
when  fed  to  animals.  Recent  investigations,  however, 
show  that  there  is  no  alkaloidal  material  in  oats,  and 
whatever  stimulating  effect  they  may  have  results  from 
the  nutrients  they  contain.  Occasionally  there  is  an 
appreciable  amount  of  cellulose,  or  fiber,  left  in  the  oat 
preparations,  due  to  imperfect  milling.  This  noticeably 
lowers  the  digestibility.  Oatmeal  requires  much  longer 


CEREALS 


125 


and  more  thorough  cooking  than  many  other  cereals, 
and  it  is  frequently  used  as  food  when  not  well  pre- 
pared. Digestion  experiments  show  that  when  oatmeal 
is  cooked  for  four  hours  or  more,  it  is  mo?£  readily  acted 
upon  by  the  diastase  ferment  and  digested  in  a  shorter 


FIG.  32. —  OAT  STARCH  GRANULES. 

time  than  oatmeal  cooked  only  a  half  hour.5  Oatmeal 
is  one  of  the  cheapest  sources  from  which  protein  is 
obtained,  and  when  well  cooked  it  can  advantageously 
form  an  essential  part  of  the  ration.  Unless  thoroughly 
cooked,  the  oat  preparations  do  not  appear  to  be  quite  so 
completely  or  easily  digested  as  some  of  the  other  cereals. 


126      HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

146.  Wheat  Preparations  differ  in  chemical  composi- 
tion more  than  those  from  oats  or  corn,  because  wheat 
is  prepared  in  a  greater  variety  of  ways.  They  are 
made  either  from  the  entire  kernel,  including  the  bran 


FIG.  33.  — WHEAT  STARCH  GRAINS. 

and  germ,  or  from  special  parts,  as  the  granular  mid- 
dlings, as  in  the  case  of  some  of  the  breakfast  foods,  and 
a  few  are  made  into  a  dough  and  baked,  then  dried  and 
toasted.  Some  special  flours  are  advertised  as  com- 
posed largely  of  gluten,  but  only  those  that  have  been 
prepared  by  washing  out  the  starch  are  entitled  to  be 
classed  as  gluten  flours.58  For  the  food  of  persons 


CEREALS  127 

suffering  from  diabetes  mellitus  physicians  advise  the 
use  of  flour  low  in  starch,  and  this  can  be  made  by 
washing  and  thus  removing  a  portion  of  the  starch  from 
wheat  flour,  as  directed  in  Experiment  No.  30.  The 
glutinous  residue  is  then  used  for  preparing  articles  of 
food.  Analyses  of  some  of  the  so-called  gluten  flours 
show  that  they  contain  no  more  gluten  than  ordinary 
flour,  particularly  the  low  grades.  A  number  of  wheat 
breakfast  foods  are  prepared  by  sterilizing  the  flour 
middlings  obtained  after  removal  of  the  bran  and  germ. 
These  middlings  are  the  same  stock  or  material  from 
which  the  patent  grades  of  flour  are  made,  and  they 
differ  from  wheat  flour  only  in  mechanical  structure 
and  size  of  the  particles.  Where  granular  wheat  mid- 
dlings can  be  secured  in  bulk  at  the  same  price  as 
flour  they  furnish  a  valuable  and  cheap  cereal  breakfast 
food. 

As  to  the  digestibility  and  food  value,  the  wheat 
breakfast  foods  have  practically  the  same  as  graham, 
entire  wheat,  or  ordinary  patent  flour,  depending  upon 
the  stock  which  they  contain.  Those  with  large  amounts 
of  bran  and  germ  are  not  as  completely  digested  as 
when  these  parts  of  the  kernel  are  not  included.  Wheat 
preparations,  next  to  oats,  have  the  most  protein  of  any  of 
the  cereal  foods.  Occasionally  they  are  prepared  from 
wheats  low  in  gluten  and  not  suitable  for  bread-making 
purposes.  When  purchased  in  bulk  the  wheat  prepara- 
tions are  among  the  cheapest  foods  that  can  be  used  in 
the  dietary.56 


: 


128      HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 


147.  Barley  Preparations  are  not  so  extensively  used 
as  wheat,  oats,  and  corn.  Barley  contains  a  little  more 
protein  than  corn,  but  not  quite  so  much  as  wheat; 
otherwise  it  is  quite  similar  to  wheat  in  general  composi- 
tion. Sometimes  in  the  preparation  of  breakfast  foods 


FIG.  34.  —  BARLEY  STARCH. 

barley  meal  is  mixed  with  wheat  or  corn.  Barley  is 
supposed  to  be  more  readily  digested  than  some  of  the 
other  cereals,  because  of  the  presence  of  larger  amounts 
of  active  ferment  bodies,  and  it  is  frequently  used  for 
making  an  extract  known  as  "  barley  water,"  which, 
although  it  contains  very  little  nutritive  value,  as  less 


CEREALS 


I2Q 


than  one  per  cent  of  the  weight  of  the  barley  is  rendered 
soluble,  is  useful  in  its  soothing  influence  and  mechan- 
ical action  upon  the  mucous  membrane  of  the  digestive 
tract. 


v«J  -fw'.^y  W^f^ 


FIG.  35.  — RICE  STARCH. 

148.  Rice  Preparations.  —  Rice  varies  somewhat  in 
composition,  but  usually  contains  a  slightly  lower  per- 
centage of  protein  than  corn  and  also  a  smaller  amount 
of  fat.  It  is  particularly  rich  in  starch,  and  has  the  least 


130       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


ash  or  mineral  matter  of  any  of  the  cereals.  In  order 
to  make  a  balanced  ration,  rice  should  be  supplemented 
with  legumes  and  other  foods  rich  in  proteids.  It  is  a 
valuable  grain,  but  when  used  alone  it  is  deficient  in 
protein.  Rice  is  digested  with  moderate  ease,  but  is  not 
as  completely  absorbed  by  the  body  as  other  cereals, 
particularly  those  prepared  by  fine  grinding  or  pulver- 
ization. Of  late  years  rice  culture  has  been  extensively 
introduced  into  some  of  the  southern  states,  and  the  do- 
mestic rice  seems  to  have  slightly  higher  protein  content: 
than  the  imported.  Rice  contains  less  protein  than 
other  cereals,  and  the  starch  grain  is  of  different  con- 
struction. Rice  does  not  require  such  prolonged  cook- 
ing as  oatmeal;  it  needs,  however,  to  be  thoroughly 
cooked. 

149.    Predigested  Foods.56 

"  It  is  questionable  whether  it  would  be  of  advantage  to  a  healthy 
person  to  have  his  food  artificially  digested.  The  body  under  nor- 
mal conditions  is  well  adapted  to  utilize  such  foods  as  the  ordinary 
mixed  diet  provides,  among  them  the  carbohydrates  from  the  cereals. 
Moreover,  it  is  generally  believed  that  for  the  digestive  organs,  as 
for  all  others  of  the  body,  the  amount  of  exercise  they  are  normally 
fitted  to  perform  is  an  advantage  rather  than  the  reverse.  It  has 
been  said  that  *a  well  man  has  no  more  need  of  predigested  food 
than  a  sound  man  has  for  crutches.1  If  the  digestive  organs  are  out 
of  order,  it  may  be  well  to  save  them  work,  but  troubles  of  digestion 
are  often  very  complicated  affairs,  and  the  average  person  rarely  has 
the  knowledge  needed  to  prescribe  for  himself.  In  general,  those  who 
are  well  should  do  their  own  work  of  digestion,  and  those  who  are 
ill  should  consult  a  competent  physician."  —  WOODS  AND  SNYDER. 


CEREALS  131 

150.  The  Value  of  Cereals  in  the  Dietary.  —  Cereals 
are  valuable  in  the  dietary  because  of  the  starch  and 
protein  they  supply,  and  the  heat  and  energy  they  yield. 
They  are  among  the  most  inexpensive  of  foods  and, 
when  properly  prepared,  have  a  high  degree  of  palata- 
bility ;  then,  too,  they  are  capable  of  being  blended  in 
various  ways  with  other  foods.  Some  are  valuable  for 
their  mechanical  action  in  digestion,  rather  than  for  any 
large  amount  of  nutrients.  They  do  not  furnish  the 
quantity  of  mineral  matter  and  valuable  phosphates  that 
is  popularly  supposed.  They  all  contain  from  0.5  to  1.5 
per  cent  of  mineral  matter,  of  which  about  one  third  is 
phosphoric  anhydrid.  In  discussing  the  phosphate  con- 
tent of  food,  Hammersten  states  :59 

"  Very  little  is  known  in  regard  to  the  need  of  phosphates  or 
phosphoric  acid.  .  .  .  The  extent  of  this  need  is  most  difficult  to 
determine,  as  the  body  shows  a  strong  tendency,  when  increased 
amounts  of  phosphorus  are  introduced,  to  retain  more  than  is  neces- 
sary. The  need  of  phosphates  is  relatively  smaller  in  adults  than 
in  young  developing  animals." 

In  the  coarser  cereals,  which  include  the  bran  and 
germ,  there  is  the  maximum  amount  of  mineral  matter, 
but,  as  in  the  case  of  graham  bread,  it  is  not  as  completely 
digested  and  absorbed  by  the  body  as  the  more  finely 
granulated  products  which  contain  less.  The  kind  of 
cereal  to  use  in  the  dietary  is  largely  a  matter  of  per- 
sonal choice.  As  only  a  small  amount  is  usually  eaten 
at  a  meal,  there  is  little  difference  in  the  quantity  of 
nutrients  supplied  by  the  various  breakfast  cereals. 


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132 


CHAPTER   X 
WHEAT  FLOUR 

151.  Use  for  Bread  Making.  —  Wheat  is  particularly 
adapted  to  bread-making  purposes  because  of  the  physi- 
cal properties  of  the  gliadin,  one  of  its  proteids.     It  is 
the  gliadin   which,  when  wet,  binds  together  the  flour 
particles,  enabling  the  gas  generated  during  bread  mak- 
ing to  be  retained,  and  the  loaf  to  expand  and  become 
porous.     Wheat  varies  in  chemical  composition  between 
wide  limits;  it  may  contain  as  high  as   16  per  cent  of 
protein,  or  as  low  as  8  per  cent ;  average  wheat  has  from 
12  to  14  per  cent;  and  with  these  differences  in  compo- 
sition,- the  bread-making  value  varies. 

152.  Winter  and  Spring  Wheat  Flours.  —  There   are 
two  general  classes  of  wheat :  spring  wheat  and  winter 
wheat.     The  winter  varieties  are  seeded  in  the  fall,  and 
the  spring  varieties,  which  are    grown    mainly   in    the 
Northwestern  states,  Minnesota,  and  North  and  South 
Dakota,  and  the  Canadian  Northwest,  are  seeded  in  the 
spring  and  mature  in  the  late  summer.     Winter  wheat 
is  confined   to  more  southern  latitudes  and  regions  of 
less  severe  winter,  and  matures  in  the  early  summer. 
There  are  many  varieties   of  both   spring  and  winter 

133 


134       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


FIG.  36. — STARCHY  (LIGHT-COLORED)  AND  GLUTINOUS 
(DARK-COLORED)  WHEATS. 


WHEAT    FLOUR 


135 


wheat,  although  wheats  are  popularly  characterized  only 
as  hard  or  soft,  depending  upon  the  physical  proper- 
ties. The  winter  wheats 
are,  as  a  rule,  more  soft 
and  starchy  than  the  spring 
wheats,  which  are  usually 
corneous  or  flinty  to  differ- 
ent degrees.  There  is  a 
general  tendency  for 
wheats  to  become  either 
starchy  or  glutinous,  owing 
to  inherited  individuality  of 
the  seed  and  to  environ- 
ment. There  are  often 
found  in  the  same  field 
wheat  plants  yielding  hard 
glutinous  kernels,  and  other 
plants  producing  starchy 
kernels  containing  5  per 
cent  less  proteids.  Wheats 
of  low  protein  content  do 
not  make  high-grade  flour  ; 
neither  do  wheats  of  the 
maximum  protein  content  necessarily  make  the  best 
flour.  For  a  more  extended  discussion  of  wheat  pro- 
teids, the  student  is  referred  to  Chapter  XL 

153.    Composition  of  Wheat  and  Flour.  —  In  addition 
to  12  to  14  per  cent  proteids,  wheat  contains  72  to  76 


FIG.  37.  —  LONGITUDINAL  SECTION 
OF  WHEAT  KERNEL  :  a,  pericarp ; 
b,  bran  layers ;  c,  aleurone  cells ; 
dt  germ.  (After  KONIG.) 


136      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


per  cent  of  starch  and  small  amounts  of  other  carbohy- 
drates, as  sucrose,  dextrose,  and  invert  sugar.  The 
ash  or  mineral  matter  ranges  from  1.7  to  2.3  per  cent. 
There  is  also  about  2  per  cent  fiber,  2.25  per  cent  ether 
extract  or  crude  fat,  and  about  0.2  per  cent  organic 
acids. 


Summary : 


COMPOSITION  OF  WHEAT  FLOUR 


Water   . 

Ash 

Protein< 

Other  ni 
Crude  fa 
Cellulose 
Starch   . 

Per  Cent 
12.00 

2.25 

13.00 

0.25 
2.25 
2.25 

66.00 

2.00 

Potash 
Soda 
Lime 
Magnesia 
Phosphoric  anhydrid 
Sulphuric  anhydrid 
Other  substances 
Albumin                 0.4 
Globulin                 0.9 
Gliadin                   6.0 
Glutenin                 5.3 
Other  proteids       0.4 
trogenous  bodies,  as  a 
t,  ether  extract 

mids,  lecethin      .... 

Sucrose,  dextrose,  soluble  carb 

ohydrates  etc. 

0. 


154.  Roller  Process  of  Flour  Milling.  —  Flours  vary 
in  composition,  food  value,  and  bread-making  qualities 
with  the  character  of  the  wheat  and  the  process  of 


WHEAT    FLOUR 


137 


milling  employed.  Prior  to  1870  practically  all  wheat 
flour  was  prepared  by  grinding  the  wheat  between  mill- 
stones ;  but  with  the  introduction  of  the  roller  process, 


FIG.  38.  — GRANULAR  WHEAT  FLOUR  PARTICLES. 

steel  rolls  were  substituted  for  millstones.60  By  the  for- 
mer process  a  smaller  amount  of  flour  was  secured  from 
the  wheat,  but  with  the  present  improved  systems  about 


138       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

75  per  cent  of  the  weight  of  the  grain  is  recovered  as 
merchantable  flour  and  25  per  cent  as  wheat  offals, 
bran,  and  shorts.61 

The  wheat  is  first  screened  and  cleaned,  then  passed 
on  to  the  corrugated  rolls,  or  the  first  break,  where 
it  is  partially  flattened  and  slightly  crushed  and  a 
small  amount  of  flour,  known  as  the  break  flour, 
is  separated  by  means  of  sieves,  while  the  main  portion 
is  conveyed  through  elevators  to  the  second  break, 
where  the  kernels  are  more  completely  flattened  and 
the  granular  flour  particles  are  partially  separated 
from  the  bran.  The  material  passes  over  several 
pairs  of  rolls  or  breaks,  each  succeeding  pair  being 
set  a  little  nearer  together.  This  is  called  the  gradual 
reduction  process,  because  the  wheat  is  not  made 
into  flour  in  one  operation.  More  complete  removal 
of  the  bran  and  other  impurities  from  the  middlings 
is  effected  by  means  of  sieves,  aspirators,  and  other 
devices,  and  the  purified  middlings  are  then  passed 
on  to  smooth  rolls,  where  the  granulation  is  completed. 
The  flour  finally  passes  through  silk  bolting  cloths, 
containing  upwards  of  12,000  meshes  per  square  inch. 
The  dust  and  fine  debris  particles  are  removed  at 
various  points  in  the  process.  The  granulation  of  the 
middlings  is  done  after  the  impurities  are  removed,  the 
object  being  first  to  separate  as  perfectly  as  pos- 
sible the  middlings  from  the  branny  portions  of  the 
kernel.  If  the  wheat  were  first  ground  into  a  fine 
meal,  it  would  be  impossible  to  secure  complete  sepa- 


o 
w 

i-t 

W 
I 


139 


140      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

ration    of    the   flour   from   the    offal    portions    of    the 
kernel. 

Flour  milling  is  entirely  a  mechanical  process;  the 
flour  stock  passes  from  roll  to  roll  by  means  of  eleva- 
tors. According  to  the  number  of  reductions  which  the 
middlings  and  stock  undergo,  the  milling  is  designated  as  a 
long  or  a  short  reduction  system ;  the  term  4,  6,  8,  or  10 
break  process  means  that  the  stock  has  been  subjected 
to  that  number  of  reductions.  With  an  8-break  system 
of  milling,  the  process  is  more  gradual  than  with  a 
4-break,  and  greater  opportunity  is  afforded  for  complete 
removal  of  the  bran.  In  some  large  flour  mills,  the 
wheat  is  separated  into  forty  or  more  different  products, 
or  streams,  as  they  are  called,  so  as  to  secure  a  better 
granulation  and  more  complete  removal  of  the  offals, 
after  which  many  of  these  streams  are  brought  together 
to  form  the  finished  flour.  What  is  known  as  patent  flour 
is  derived  from  the  reduction  of  the  middlings,  while 
the  break  flours  are  recovered  before  the  offals  are 
completely  removed ;  hence  they  are  not  of  so  high 
a  grade.  No  absolute  definition  can  be  given,  how- 
ever, of  the  term  "patent  flour,"  as  usage  varies  the 
meaning  in  different  parts  of  the  country. 

155.  Grades  of  Flour.  —  Flour  is  the  purified,  refined, 
and  bolted  product  obtained  by  reduction  and  granu- 
lation of  wheat  during  and  after  the  removal  of  the 
branny  portions  of  the  wheat  kernel.  It  is  defined  by 
proclamation  of  the  Secretary  of  Agriculture,  under 


o 
U 


w 

I 


K-J 

§ 


O 

I 
i 


141 


142       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

authority  of  an  act  of  Congress,  as :  "  Flour  is  the 
fine,  sound  product  made  by  bolting  wheat  meal,  and 
contains  not  more  than  thirteen  and  one  half  (13.5) 
per  cent  of  moisture,  not  less  than  one  and  twenty- 
five  hundredths  (1.25)  per  cent  of  nitrogen,  not  more 
than  one  (i)  per  cent  of  ash,  and  not  more  than  fifty 
hundredths  (0.50)'  per  cent  of  fiber." 

Generally  speaking,  flour  may  be  divided  into  two 
classes,  high  grade  and  low  grade.  To  the  first  class 
belong  the  first  and  second  patents  and,  according  to 
some  authorities,  a  portion  of  the  straight  grade,  or 
standard  patent  flour,  and  to  the  second  class  belong 
the  second  clear  and  "red  dog."  About  72  per  cent 
of  the  cleaned  wheat  as  milled  is  recovered  in  the 
higher  grades  of  flour,  and  about  2  or  3  per  cent  as  low 
grades,  a  large  portion  of  which  is  sold  as  animal  food. 
The  high  grades  are  characterized  by  a  lighter  color, 
more  elastic  gluten,  better  granulation,  and  a  smaller 
number  of  debris  particles.  Although  the  lower  grade 
flours  contain  a  somewhat  higher  percentage  of  protein, 
they  are  not  as  valuable  for  bread-making  purposes 
because  the  gluten  is  not  as  elastic,  and  consequently 
they  do  not  make  as  good  bread.  If  the  impurities 
from  the  low  grades  could  be  further  eliminated,  it  is 
believed  that  less  difference  would  exist  between  high 
and  low  grade  flours. 

Various  trade  names  are  used  to  designate  flours,  as 
a  95  per  cent  patent,  meaning  that  95  per  cent  of  the 
total  flour  is  included  in  the  patent;  or  an  85  per  cent 


WHEAT   FLOUR 


143 


patent,  when  85  per  cent  of  all  the  flour  is  included  in 
that  particular  patent.  If  all  the  flour  streams  were 
purified  and  blended,  and  only  one  grade  of  flour  made, 


»m  w 


»•  m.m-m 


1  m  9 


«*«§«• 


m  m 


FIG.  41. — SILK  BOLTING  CLOTH  USED  IN  MANUFACTURE  OF  FLOUR, 
MAGNIFIED. 


it  would  be  called  a  100  per  cent  patent.  An  85  per 
cent  patent  is  a  higher  grade  flour  than  a  95  per  cent 
patent. 

156.  Composition  of  Flour.  —  The  composition  of  the 
different  grades  of  flour  made  from  the  same  wheat  is 
given  in  the  following  table  : 62 


; 


144      HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 


COMPOSITION,  ACIDITY,  AND  HEATS  OF  COMBUSTION  OF  FLOURS 
AND  OTHER  MILLED  PRODUCTS  OF  WHEAT 


MILLED  PRODUCT 

M 
H 

H 

$ 

3    IT) 

H 

CARBO- 
HYDRATES 

K 

ACIDITY 
CALCULATED 
AS  LACTIC 
ACID 

HEAT  OF 
COMBUSTION 
PER  GRAM 
DETERMINED 

% 

% 

% 

% 

% 

% 

Calories 

First  patent  flour     .     . 

10.55 

11.08 

I.I5 

76.85 

0-37 

0.08 

4032 

Second  patent  flour 

10.49 

11.14 

1.  2O 

76.75 

0.42 

0.08 

4006 

Straight  *    or  standard 

patent  flour     .     .     . 

10.54 

11.99 

1.61 

75-36 

0.50 

0.09 

4050 

First  clear  grade  flour  . 

10.13 

13-74 

2.  2O 

73-13 

0.80 

O.I  2 

4097 

Second  clear  grade  flour 

10.08 

15.03 

3-77 

69.37 

i-75 

0.56 

4267 

"Red  dog"  flour      .     . 
Shorts    

9.17 

8.73 

18.98 
14.87 

7.00 
637 

61.37 
6  £.47 

4..  56 

O.I4 

4485 

4414. 

Bran            

Q  QQ 

I4.O2 

6c  .  c|4 

606 

O.23 

4.10,8 

Entire-wheat  flour   . 

y  yy 
I0.8I 

12.26 

2.24 

1.02 

0.32 

4032 

Graham  flour  .... 
-Wheat    

8.61 

8.50 

12.65 

2.44 

74.58 
74..  60 

1.72 
1.  80 

0.18 
0.18 

4148 
4.I4.O 

In  the  table  it  will  be  noted  that  there  is  a  gradual 
increase  in  protein  content  from  first  patent  to  "red 
dog,"  the  largest  amount  being  in  the  "red  dog"  flour. 
Although  "red  dog"  contains  the  most  protein,  it  is  by 
far  the  poorest  flour  in  bread-making  qualities,  and  in 
the  milling  of  wheat  often  it  is  not  separated  from  the 
offals,  but  is  sold  as  an  animal  food.  It  will  also  be 
seen  that  there  is  a  gradual  increase  in  the  ash  content 
from  the  highest  to  the  lowest  grades  of  flour,  the 

*  Straight  flour  includes  the  first  and  second  patents  and  first  clear  grade. 


WHEAT    FLOUR  145 

increase  being  practically  proportional  to  the  grade, — 
the  most  ash  being  in  the  lowest  grade.  The  grade  to 
which  a  flour  belongs  can  be  determined  more  accu- 
rately from  the  ash  content  than  from  any  other  constit- 
uent. Patent  grades  of  flour  rarely  contain  more  than 
0.55  per  cent  of  ash,  —  the  better  grades  less  than  0.5  per 
cent.  The  more  completely  the  bran  and  offals  are  re- 
moved during  the  process  of  milling,  the  lower  the  per 
cent  of  ash.  The  ash  content,  however,  cannot  be 
taken  as  an  absolute  guide  in  all  cases,  as  noticeable 
variations  occur  in  the  amount  of  mineral  matter  or  ash 
in  different  wheats ;  starchy  wheats  that  have  reached 
full  maturity  often  contain  less  than  hard  wheats  grown 
upon  rich  soil  where  the  growing  season  has  been  short, 
and  from  such  wheats  a  soft,  straight  flour  may  have 
as  low  a  per  cent  of  ash  as  a  hard  first  patent  flour. 
When  only  straight  or  standard  patent  flour  is  manufac- 
tured by  a  mill,  all  of  the  flour  is  included  which  would 
otherwise  be  designated  first  and  second  patents  and 
first  clear. 

157.  Graham  and  Entire  Wheat  Flours.  —  When  the 
germ  and  a  portion  of  the  bran  are  retained  in  the 
flour,  and  the  particles  are  not  completely  reduced,  the 
product  is  called  "  entire  wheat  flour/'  The  name  does 
not  accurately  describe  the  product,  as  it  includes  all  of 
the  flour  and  only  a  portion  of  the  bran,  and  not  the 
entire  wheat  kernel.  Graham  flour  is  coarsely  granu- 
lated wheat  meal.  No  sieves  or  bolting  cloths  are 


146      HUMAN    FOODS    AND   THEIR    NUTRITIVE 


VALUE 


employed  in  its  manufacture,  and  many  coarse,  unpul- 
verized  particles  are  present  in  the  product.62 

158.  Composition  of  Wheat  Offals.  —  Bran  and  shorts 
are  characterized  by  a  high  percentage  of  fiber,  or  cel- 
lulose. The  ash,  fat,  and  protein  content  of  bran  are  all 
larger  than  of  flour.  The  protein,  however,  is  not  in  the 
form  of  gluten,  but  is  largely  albumin  and  globulins,16 


i  234 

FIG.  42.  — FLOUR  AND  GLUTEN. 
i,  flour ;  2,  dough ;  3,  moist  gluten ;  4,  dry  gluten. 

which  are  mainly  in  the  aleurone  layer  of  the  wheat 
kernel,  and  are  inclosed  in  branny  capsules,  and  conse- 
quently are  in  a  form  not  readily  digested  by  man. 

The  germ  is  generally  included  in  the  shorts,  although 
occasionally  it  is  removed  for  special  commercial  pur- 
poses. It  is  sometimes  sterilized  and  used  in  breakfast 
food  products.  The  germ  is  rich  in  oil  and  is  excluded 
from  the  flour  mainly  because  it  has  a  tendency  to  be- 
come rancid  and  to  impart  to  the  flour  poor  keeping 


WHEAT    FLOUR  147 

qualities.  Wheat  oil  has  cathartic  properties,  and  it  is 
believed  the  physiological  action  of  whole  wheat  and 
graham  bread  is  in  part  due  to  the  oil.  The  germ  is 
also  rich  in  protein,  mainly  in  the  form  of.  globulins  and 
proteoses.  A  dough  cannot  be  made  of  pure  germ, 
because  it  contains  so  little  of  the  gliadin  and  glutenin. 

159.  Aging  and  Curing  of  Flour.  —  Flours  well  milled 
and  made  from  high-grade,  cleaned  wheat  generally 
improve  in  bread-making  value  when  stored  in  clean, 
ventilated  warehouses  for  periods  of  three  to  six  months.9 
High-grade  flour  becomes  drier  and  whiter  and  pro- 
duces bread  of  slightly  better  quality  when  properly 
cured  by  storage.  If  the  flour  is  in  any  way  unsound, 
it  deteriorates  during  storage,  due  to  the  action  of  fer- 
ment bodies.  Wheat  also,  when  properly  cleaned  and 
stored,  improves  in  milling  and  bread-making  value. 
Certain  enzymic  changes  appear  to  take  place  which 
are  beneficial.  Wheats  differ  materially  from  year  to 
year  in  bread-making  value,  and  those  produced  in 
seasons  when  all  the  conditions  for  crop  growth  are 
normal,  do  not  seem  to  be  so  much  improved  by  storing 
and  aging,  either  of  the  wheat  or  the  flour,  as  when  the 
growing  season  has  been  unfavorable.  When  wheat  is 
stored,  specific  changes  occur  in  both  the  germ  and  the 
cells  of  the  kernel ;  these  changes  are  akin  to  the  ripen- 
ing process,  and  appear  to  be  greater  if,  for  any  reason, 
the  wheat  has  failed  to  fully  mature  or  is  abnormal  in 
composition. 


148        HUMAN    FOODS   AND   THEIR    NUTRITIVE    VALUE 

The  flour  yield  of  wheat  is  in  general  proportional  to 
the  weight  per  bushel  of  the  grain,  well-filled,  heavy 
grain  producing  more  flour  than  light  grain.61  The 
quality  of  the  flour,  however,  is  not  necessarily  propor- 1 
tional  to  the  weight  of  the  grain.  It  is  often  necessary 
to  blend  different  grades  and  types  of  wheat  in  order  to 
secure  good  flour. 

160.  Macaroni  Flour  is  made  from  durum  wheat,  ac- 
cording to  Saunders  a  variety  of  hard,   spring  wheat. 
It  is  best  grown  in  regions  of  restricted  rainfall.     Durum 
and  other  varieties  of  hard  spring  wheat  grown  under 
similar  conditions,  differ  but  little  in  general  chemical 
composition,  except  that  the  gluten  of  durum  appears  to 
have  a  different  percentage  of  gliadin  and  glutenin,  and 
the  flour  has  a   more   decided   yellow   color.     Durum 
wheats    are    not   generally  considered  as  valuable  for 
bread  making  as  other  hard  wheat.     They  differ  widely 
in  bread-making  value,   some   being  very  poor,   while 
others  produce  bread  of  fair  quality.63 

161.  Color. — The  highest  grades  of  flour  are  white 
in  color,  or  of   a  slight  creamy  tinge.      Dark-colored, 
slaty,  and  gray  flours  are  of  inferior  quality,  indicating 
a  poor  grade  of  wheat,  poor  milling,  or  a  poor  quality  of 
gluten.     Flours,  after  being  on  the  market  for  a  time, 
bleach  a  little  and  improve  to  a  slight  degree  in  color. 
Color  is  one  of  the  characteristics  by  which  the  com- 

"mercial  value  of  flour  is  determined;  the  whiter  the 


WHEAT    FLOUR  149 

flour,  the  better  the  grade,  provided  other  properties  are 
equal.9  The  color,  however,  should  be  a  pure  or  cream 
white.  Some  flours  have  what  is  called  a  dead  white 
color,  and,  while  not  objectionable  as  far  as  color  is  con- 
cerned, they  are  not  as  valuable  for  bread-making  and 
general  commercial  purposes.  One  of  the  principal 
trade  requirements  of  a  flour  is  that  it  possess  a  cer- 
tain degree  of  whiteness  and  none  of  the  objectionable 
shades  mentioned. 

To  determine  the  color  of  a  flour,  it  is  compared  with 
a  standard.  If  it  is  a  winter  wheat  flour,  one  of  the  best 
high-grade  winter  patents  to  be  found  on  the  market 
is  selected,  and  the  sample  in  question  is  compared  with 
this ;  if  it  is  a  spring  wheat  patent  flour,  one  of  the  best 
spring  wheat  patent  grades  is  taken  as  the  standard. 
In  making  the  comparison,  the  flours  should  be  placed 
side  by  side  on  a  glass  plate  and  smoothed  with  the 
flour  trier,  the  comparison  being  made  preferably  by  a 
north  window.  Much  experience  and  practice  are  neces- 
sary in  order  to  determine  with  accuracy  the  color  value 
of  a  flour. 

162.  Granulation.  —  The  best  patent  grades  of  flour 
contain  an  appreciable  amount  of  granular  middlings, 
which  have  a  characteristic  "  feel "  similar  to  fine,  sharp 
sand.  A  flour  which  has  no  granular  feeling  is  not  usu- 
ally considered  of  the  highest  grade,  but  is  generally 
a  soft  wheat  flour  of  poor  gluten.  However,  a  flour 
should  not  be  too  coarsely  granulated.  The  percentage 


150        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

amounts  of  the  different  grades  of  stock  in  a  flour  can  be 
approximately  determined  by  means  of  sieves  and  differ- 
ent sized  bolting  cloths.  To  test  a  flour,  ten  grams  are 
placed  in  a  sieve  containing  a  No.  10  bolting  cloth ;  with 
a  camel's-hair  brush  and  proper  manipulation,  the  flour 
is  sieved,  and  that  which  passes  through  is  weighed. 
The  percentage  amount  remaining  on  the  No.  10  cloth 
is  coarser  middlings.  Nearly  all  high-grade  flours  leave 
no  residue  on  the  No.  10  cloth.  The  sifted  flour  from 
the  No.  10  cloth  is  also  passed  through  Nos.  n,  12,  13, 
and  14  cloths.63  In  this  way  the  approximate  granula- 
tion of  any  grade  of  flour  may  be  determined,  and  the 
granulation  of  an  unknown  sample  be  compared  with 
that  of  a  standard  flour.  In  determining  the  granula- 
tion of  a  flour,  if  there  are  any  coarse  or  discolored  par- 
ticles of  bran  or  dust,  they  should  be  noted,  as  it  is  an 
indication  of  poor  milling.  When  the  flour  is  smoothed 
with  a  trier,  there  should  be  no  channels  formed  on  the 
surface  of  the  flour,  due  to  fibrous  impurities  caught 
under  the  edge  of  the  trier.  A  hand  magnifying  glass 
is  useful  for  detecting  the  presence  of  abnormal 
amounts  of  dirt  or  fibrous  matter  in  the  flour. 

163.  Capacity  of  Flour  to  absorb  Water.  —  The  ca- 
pacity of  a  flour  to  absorb  water  is  determined  by  add- 
ing water  from  a  burette  to  a  weighed  amount  of  flour 
until  a  dough  of  standard  consistency  is  obtained.  Low 
absorption  is  due  to  low  gluten  content.  A  good  flour 
should  absorb  from  60  to  65  per  cent  of  its  weight  of 


WHEAT    FLOUR  151 

water.  In  making  the  test,  it  is  advisable  to  determine 
the  absorption  of  a  flour  of  known  baking  value  at 
the  same  time  that  an  unknown  flour  is  being  tested. 
Flours  of  low  absorption  do  not  make  breads  of  the  best 
quality ;  also  there  are  a  smaller  number  of  loaves  per 
barrel,  and  the  bread  dries  out  more  readily. 

164.  Physical  Properties   of  Gluten.  —  The   percent- 
ages of  wet  and  dry  gluten  in  a  flour  are  determined 
as   outlined   in    Experiment  No.  27.     Flours    of   good 
character  should  show  at  least  30  per  cent  moist  gluten 
and  from  10  to  12  per  cent  dry  gluten.     The  quality  of 
a   flour   is   not   necessarily  proportional    to    its    gluten 
content,  although  a  flour  with  less  than   10^  per  cent 
of  dry  gluten  will  not  make  the  best  quality  of  bread, 
and  flours  with  excessive  amounts  are  sometimes  poor 
bread  makers.     The  color  of  the  gluten  is  also  impor- 
tant;   it  should  be  white  or  creamy.     The  statements 
made  in  regard  to  color  of  flour  apply  also  to  color  of 
the   gluten.     A  dark,    stringy,   or   putty-like  gluten    is 
of  little  value  for   bread-making  purposes.64     In  mak- 
ing  the    gluten   test,    it   is   advisable  to  compare   the 
gluten  with  that  from  a  flour  of  known  bread-making 
value.     Soft   wheat   flours   have   a  gluten  of  different 
character  from  hard  wheat  flours. 

165.  Gluten   as   a  Factor   in   Bread   Making.  —  The 

bread-making  value  of  a  flour  is  dependent  upon  the 
character  of  the  wheat  and  the  method  of  milling.  It 


152       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

is  not  necessarily  dependent  upon  the  amount  of 
gluten,  as  the  largest  volume  and  best  quality  of  bread 
are  often  made  from  flour  of  average  rather  than  maxi- 
mum gluten  content.  But  flours  with  low  gluten  do 
not  produce  high-grade  breads.  When  a  flour  con- 
tains more  than  12  or  13  per  cent  of  proteids,  any  in- 
crease does  not  necessarily  mean  added  bread-making 
value.  The  quality  of  the  gluten,  equally  with  the 
amount,  determines  the  value  for  bread-making  pur- 
poses. 

166.  Unsoundness. — A  flour  with  more  than  14  per 
cent  of  moisture  is  liable  to  become  unsound.  High 
acidity  also  is  an  indication  of  unsoundness  or  of 
poor  keeping  qualities.  The  odor  of  a  sample  of  flour 
should  always  be  carefully  noted,  for  any  suggestion 
of  fermentation  sufficient  to  affect  the  odor  renders 
the  flour  unsuited  for  making  the  best  bread.  Any 
abnormal  odor  in  flour  is  objectionable,  as  it  is  due  to 
contamination  of  some  sort,  and  most  frequently  to 
fermentation  changes.  A  musty  odor  is  always  an 
indication  of  unsoundness.  Some  flours  which  have 
but  a  slight  suggestion  of  mustiness  will,  when  baked 
into  bread,  have  it  more  pronounced ;  on  the  other 
hand,  some  odors  are  removed  during  bread  making. 
Flours  may  absorb  odors  because  of  being  stored  in 
contaminated  places  or  being  shipped  in  cars  in  which 
oil  or  other  ill-smelling  products  with  strong  odors 
have  previously  been  shipped.  Unsoundness  is  often 


WHEAT    FLOUR  153 

due  to  faulty  methods  in  handling,  as  well  as  to  poor 
wheat,  or  to  lack  of  proper  cleaning  of  the  wheat  or 
flour. 


FIG.  43.  —  FUNGOUS  GROWTH  IN  UNSOUND  FLOUR. 

167.  Comparative  Baking  Tests.  —  To  determine  the 
bread-making  value  of  a  flour,  comparative  baking 
tests,  as  outlined  in  Experiment  No.  29,  are  made ; 
the  flour  in  question  is  thus  compared  as  to  bread- 


154      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

making  value  with  a  flour  of  known  baking  quality. 
In  making  the  baking  tests,  the  absorption  of  the 
flour,  the  way  in  which  it  responds  in  the  doughing 
process,  and  the  general  properties  of  the  dough,  are 
noted.  The  details  should  be  carried  out  with  care, 


FIG.  44.  — COMPARATIVE  BAKING  TESTS. 

the  comparison  always  being  made  with  a  similar  flour 
of  known  baking  value,  and  the  bread  should  be  baked 
at  the  same  time  and  under  the  same  conditions  as  the 
standard.  The  color  of  the  bread,  the  size  and  weight 
of  the  loaf,  and  its  texture  and  odor,  are  the  principal 
characteristics  to  be  noted. 

The  quality  of  flour  for  bread-making  purposes  is  not 


WHEAT    FLOUR  155 

strictly  dependent  upon  any  one  factor,  but  appears  to 
be  the  aggregate  of  a  number  of  desirable  character- 
istics. The  commercial  grade  of  a  flour  can  be  ac- 
curately determined  from  the  color,  granulation,  absorp- 
tion, gluten  and  ash  content,  and  the  quality  of  the  bread. 
Technical  flour  testing  requires  much  experience  and 
a  high  degree  of  skill. 

168.  Bleaching.  —  In  the  process  of  manufacture, 
flours  are  often  subjected  to  air  containing  traces  of 
nitrogen  peroxide  gas,  generated  by  electrical  action 
and  resulting  in  the  union  of  the  oxygen  and  nitrogen  of 
the  air.  This  whitens  and  improves  the  color  of  the 
flour.  Bleached  flours  differ  neither  in  chemical  com- 
position nor  in  nutritive  value  from  unbleached  flours, 
except  that  bleached  flours  contain  a  small  amount  (about 
one  part  to  one  million  parts  of  flour)  of  nitrite  react- 
ing material,  which  is  removed  during  the  process  of 
bread  making.  The  amount  of  nitrites  produced  in 
flour  during  bleaching  is  less  than  is  normally  present 
in  the  saliva,  or  is  found  naturally  in  many  vegetable 
foods,  or  in  smoked  or  cured  meats,  or  in  bread  made 
from  unbleached  flour  and  baked  in  a  gas  oven  where 
nitrites  are  produced  from  combustion  of  the  gas. 
The  bleaching  of  flour  cannot  be  regarded  as  in  any 
way  injurious  to  health  or  as  adulteration,  and  a 
bleached  flour  which  has  good  gluten  and  bread-making 
qualities  is  entirely  satisfactory.  It  is  not  possible  to 
successfully  bleach  low-grade  flours  so  .  they  will  re- 


156       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

semble  the  high  grades,  because  the  bran  impurities 
of  the  low  grades  blacken  during  bleaching  and  be- 
come more  prominent.  Alway,  of  the  Nebraska  Experi- 
ment Station,  has  shown  that  there  is  no  danger  to 
apprehend  from  over-bleaching,  for  when  excess  of 
the  bleaching  reagent  is  used,  flours  become  yellow 
in  color.65  Similar  results  have  been  obtained  at  the 
Minnesota  Experiment  Station.  As  bleaching  is  not 
injurious  to.  health,  and  as  it  is  not  possible  through 
bleaching  to  change  low  grades  so  as  to  resemble  the 
patent  grades,  bleaching  resolves  itself  entirely  into  the 
question  of  what  color  of  flour  the  consumer  desires: 

Pending  the  settle- 
ment of  the  status  of 
bleaching  the  practice 
has  been  largely  dis- 
continued. 

169.  Adulteration  of 
Flour.  —  Flour  is  not 
easily  adulterated,  as 
the  addition  of  any  for- 
eign material  interferes 
with  the  expansion  and 

bread-making  qualities 
FIG.  45.  —  WHEAT  HAIRS  AND  DEBRIS  ,     , 

IN  Low  GRADE  FLOURS.  and    hence    is    readily 

detected.     The  mixing 

of  other  cereals,  as  corn  flour,  with  wheat  flour  has  been 
attempted  at  various  times  when  wheat  commanded  a 


WHEAT   FLOUR  157 

high  price,  but  this  also  is  readily  detected,  by  micro- 
scopic examination,  as  the  corn  starch  and  wheat 
starch  grains  are  quite  different  in  mechanical  struc- 
ture. Such  flours  are  required  to  be  labeled,  in  accord 
with  the  congressional  act  of  1898,  when  Congress 
passed,  in  advance  of  the  general  pure  food  bill,  an 
act  regulating  the  labeling  and  sale  of  mixed  and 
adulterated  flours.  Various  statements  have  been 
made  in  regard  to  the  adulteration  of  flour  with  min- 
erals, as  chalk  and  barytes,  but  such  adulteration  does 
not  appear  to  be  at  all  general. 

170.  Nutritive  Value  of  Flour.  —  From  a  nutritive 
point  of  view,  wheat  flour  and  wheat  bread  have  a  high 
value.66  A  larger  amount  of  nutrients  can  be  secured 
for  a  given  sum  of  money  in  the  form  of  flour  than 
of  any  other  food  material  except  corn  meal.  Accord- 
ing to  statistics,  the  average  per  capita  consumption  of 
wheat  in  the  United  States  is  about  4^  bushels,  or, 
approximately,  one  barrel  per  year,  and  from  recent 
investigations  it  would  appear  that  the  amount  of  flour 
used  in  the  dietary  is  on  the  increase.  According  to 
the  Bureau  of  Labor,  flour  costs  the  average  laborer 
about  one  tenth  as  much  as  all  other  foods  combined, 
although  he  secures  from  it  a  proportionally  larger 
amount  of  nutritive  material  than  from  any  other 
food. 


CHAPTER  XI 
BREAD  AND   BREAD   MAKING 

171.  Leavened  and  Unleavened  Bread. —  To  make 
unleavened  bread  the  flour  is  moistened  and  worked 
into  a  stiff  dough,  which  is  then  rolled  thin,  cut  into 
various  shapes,  and  baked,  forming  a  brittle  biscuit  or 
cracker. 

The  process  of  making  raised  or  leavened  bread  con- 
sists, in  brief,  of  mixing  the  flour  and  water  in  proper 
proportions  for  a  stiff  dough,  together  with  some  salt  for 
seasoning,  and  yeast  (or  other  agent)  for  leavening.  The 
moistened  gluten  of  the  flour  forms  a  viscid,  elastic, 
tenacious  mass,  which  is  thoroughly  kneaded  to  distrib- 
ute the  yeast.  The  dough  is  then  set  in  a  warm  place 
and  the  yeast  begins  to  grow,  or  "work,"  causing  alco- 
holic fermentation,  with  the  production  of  carbon  dioxid 
gas,  which  expands  the  dough,  or  causes  it  to  "  rise," 
thus  rendering  it  porous.  After  the  yeast  has  grown 
sufficiently,  the  dough  is  baked  in  a  hot  oven,  where 
further  fermentation  is  stopped  because  of  destruction 
of  the  yeast  by  the  heat,  which  also  causes  the  gas  to 
expand  the  loaf  and,  in  addition,  generates  steam.  The 
gas  and  steam  inflate  the  tenacious  dough  and  finally 

158 


BREAD    AND    BREAD    MAKING  159 

escape  into  the  oven.  At  the  same  time  the  gluten 
of  the  dough  is  hardened  by  the  heat,  and  the  mass 
remains  porous  and  light,  while  the  outer  surface  is 
darkened  and  formed  into  a  crust. 

When  the  flour  is  of  good  quality,  the  dough  well 
prepared,  and  the  bread  properly  baked,  the  loaf  has 
certain  definite  characteristics.  It  should  be  well  raised 
and  have  a  thin,  flinty  crust,  which  is  not  too  dark  in 
color  nor  too  tough,  but  which  cracks  when  broken ;  the 
crumb,  as  the  interior  of  the  loaf  is  called,  should  be 
porous,  elastic,  and  of  uniform  texture,  without  large 
holes,  and  should  have  good  flavor,  odor,  and  color. 

Meal  or  flour  from  any  of  the  cereals  may  be  used  for 
unleavened  bread,  but  leavened  bread  can  be  made  only 
from  those  that  contain  gluten,  a  mixture  of  vegetable 
proteids  which  when  moistened  with  water  becomes 
viscid,  and  is  tenacious  enough  to  confine  the  gas  pro- 
duced in  the  dough.  Most  cereals,  as  barley,  rice,  oats, 
and  corn,  some  of  which  are  very  frequently  made  into 
forms  of  unleavened  bread,  are  deficient  or  wholly  lack- 
ing in  gluten,  and  hence  cannot  be  used  alone  for 
making  leavened  bread.  For  the  leavened  bread,  wheat 
and  rye,  which  contain  an  abundance  of  gluten,  are 
best  fitted,  wheat  being  in  this  country  by  far  the  more 
commonly  used. 

172.  Changes  during  Bread  Making.  —  In  bread  mak- 
ing complex  physical,  chemical,  and  biological  changes 
occur.  Each  chemical  compound  of  the  flour  undergoes 


l6o       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

some  change  during  the  process.     The  most  important 
changes  are  as  follows":  ^ 

1.  Production  of  carbon  dioxid  gas,  alcohol,  and  solu- 
ble carbohydrates  as  the  result  of  ferment"  action. 

2.  Partial  rupturing  of  the  starch  grains  and  forma- 
tion of  a  small  amount  of  soluble  carbohydrates  due  to 
the  action  of  heat. 

3.  Production  of  lactic  and  other  organic  acids. 

4.  Formation    of   volatile    carbon    compounds,  other 
than  alcohol  and  carbon  dioxid. 

5.  Change  in  the  solubility  of  the  gluten  proteins,  due 
to  the  action  of  the  organic  acids  and  fermentation. 

6.  Changes  in  the  solubility  of  the  proteids  due  to 
the  action  of  heat,  as  coagulation  of  the  albumin  and 
globulin. 

7.  Formation   and   liberation  of   a    small  amount  of 
volatile,  nitrogenous  compounds,  as  ammonia  and  amids. 

8.  Partial  oxidation  of  the  fat. 

173.  Loss  of  Dry  Matter  during  Bread  Making.  —  As 
many  of  the  compounds  formed  during  bread  making 
are  gases  resulting  from  fermentation  action,  and  as 
these  are  volatile  at  the  temperature  of  baking,  appreci- 
able losses  necessarily  take  place.  Experiments  show 
about  2  per  cent  of  loss  of  dry  matter  under  ordinary 
conditions.  These  losses  are  not  confined  to  the  carbo- 
hydrates alone,  but  also  extend  to  the  proteids  and  other 
compounds.  When  100  pounds  of  flour  containing  10 
per  cent  of  water  and  90  per  cent  of  dry  Ynatter  are 


BREAD    AND    BREAD    MAKING  l6l 

made  into  bread,  the  bread  contains  about  88  pounds  of 
dry  matter.  In  exceptional  cases,  where  there  has  been 
prolonged  fermentation,  the  losses  exceed  2  per  cent.64 


FIG.  46.  — BREWERS'  YEAST. 

174.   Action  of  Yeast.  —  Yeast  is  a  monocellular  planti 
requiring  sugar  and  other  food  materials  for  its  nourish-! 
ment.     Under  favorable  conditions  it  rapidly  increases  \ 
by  budding,  and  as  a  result  produces  the  well-known 
alcoholic  fermentation.     It  requires  mineral  food,  as  do. 
plants  of  a  higher  order,  and  oftentimes  the  fermenta-l 
tion  process  is  checked  for  want  of  sufficient   soluble* 

M 


162       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


mineral  food.  The  yeast  plant  causes  a  number  of 
chemical  changes  to  take  place,  as  conversion  of  starch 
to  a  soluble  form  and  alcoholic  fermentation. 


C6H10O6  +  H2O  =  C6H12O6. 
C6H12O6  =  2  C2H5OH  +  2  CO2. 

Alcoholic  fermentation  cannot  occur  until  the  starch  has 

been  converted  into  dextrose  sugar.     The  yeast  plant  is 

destroyed  at  a  temperature  of  131°  F.     It  is  most  active 

from  70°  to  9Q^F.     At  a  low  temperature  it  is  less  active, 

and  when  it  freezes  the  cells  are  ruptured.     A  number 

of  different  kinds  of  fermentation  are  associated  with  the 

growth  of  the  yeast  plant,  and  there  are  many  varieties 

of  yeast,  some  of  which  are  more  active  than  others. 

/  For  bread  making  an  active  yeast  is  desirable  to  prevent 

V,  the   formation  of  acid  bodies.     If   the   work   proceeds 

quickly,    the    rising    process  is    completed   before   the 

acid  fermentation  is  far  advanced.     If  fermentation  is 

I  too  prolonged,  some  of  the  products  of  the  yeast  plant 

I  impart  an  undesirable  taste  and  odor  to  the  bread,  and 

hinder  the  development  of  the  gluten  and  expansion  of 

the  loaf. 

175.  Compressed  Yeast.  — The  yeast  most  commonly 
used  in  bread  making  is  compressed  yeast,  a  product  of 
distilleries.  The  yeast  floating  on  the  surface  of  the 
wort  is  skimmed  off  and  that  remaining  is  allowed  to 
settle  to  the  bottom,  and  is  obtained  by  running  the  wort 
into  shallow  tanks  or  settling  trays.  It  is  then  washed 


BREAD    AND    BREAD    MAKING  163 

with  cold  water,  and  the  impurities  are  removed  either 
by  sieving  through  silk  or  wire  sieves,  or,  during  the 
washing,  by  fractional  precipitation.  The  yeast  is  then 
pressed,  cut  into  cakes,  and  wrapped  in  tinfoil.  When 
fresh,  it  is  of  uniform  creamy  color,  moist,  and  of  a  firm, 
even  texture.18  It  should  be  kept  cold,  as  it  readily  de- 
composes. 

176.  Dry  Yeast  is  made  by  mixing  starch  or  meal 
with  fresh  yeast  until  a  stiff  dough  is  formed.     This  is 
then  dried,  either  in  the  sun  or  at  a  moderate  tempera- 
ture, and  cut  into  cakes.     By  drying,  many  of  the  yeast 
cells  are  rendered  temporarily  inactive,  and  so  it  is  a 
slower  acting  leaven  than  the  compressed  yeast.     A  dry 
yeast  will  keep  indefinitely. 

177.  Production  of  Carbon  Dioxid  Gas  and  Alcohol.  — 
Carbon  dioxid  and  alcohol  are  produced  in  the  largest 
amounts  of  any  of  the  compounds  formed  during  bread 
making.     When  the  alcoholic  ferments  secreted  by  the 
yeast  plant  act  upon  the  invert    sugars   and    produce 
alcoholic  fermentation,  carbon  dioxid  is  one  of  the  prod- 
ucts   formed.     Ordinarily  about    I    per  cent  of  carbon 
dioxid  gas  is  generated  and  lost  during  bread  making. 
About  equal  weights  of  carbon  dioxid  and  alcohol  are 
produced  during  the  fermentation.     In  baking,  the  al- 
cohol is  vaporized  and  aids  the  carbon  dioxid  in  expand- 
ing the  dough  and  making  the  bread  porous.      If  all  of 
the  moisture  given  off  during  bread  making  be  collected 
it  will  be  found  that  from  a  pound  loaf  of  bread  there 


164      HUMAN   FOODS    AND   THEIR  NUTRITIVE    VALUE 


are  about  40  cubic  centimeters  of  liquid ;  when  this  is 
submitted  to  chemical  analysis,  small  amounts  of  alcohol 
are  obtained.  Alcoholic  fermentation  sometimes  fails 
to  take  place  readily,  because  there  are  not  sufficient 
soluble  carbohydrates  to  undergo  inversion,  or  other 
food  for  the  yeast  plant.  Starch  cannot  be  converted 
directly  into  alcohol  and  carbon  dioxid  gas ;  it  must 


FIG.  47. — WHEAT  STARCH  GRANULES  AFTER  FERMENTATION  WITH 
YEAST,  AS  IN  BREAD  MAKING. 

first  be  changed  into  dextrose  sugars,  and  these  undergo 
alcoholic  fermentation.  Bread  gives  no  appreciable 
reaction  for  alcohol  even  when  fresh.64 

If  the  gluten  is  of  poor  quality,  or  deficient  in  either 
gliadin  or  glutenin,  the  dough  mass  fails  to  properly 
expand  because  the  gas  is  not  all  retained.  The  amount 
of  gas  formed  is  dependent  upon  temperature,  rapidity 
of  the  ferment  action,  and  quality  of  the  yeast  and  flour. 
If  the  yeast  is  inactive,  other  forms  of  fermentation  than 


BREAD    AND    BREAD    MAKING  165 

the  alcoholic  may  take  place  and,  as  a  result,  the  dough 
does  not  expand.  Poor  yeast  is  a  frequent  cause  of  poor 
bread. 

The  temperature  reached  in  bread  making  is  not 
sufficient  to  destroy  all  the  ferment  bodies  associated 
with  the  yeast,  as,  for  example,  bread  sometimes  be- 
comes soft  and  stringy,  due  to  fermentation  changes 
after  the  bread  has  been  baked  and  stored.  Both  bread 
and  flour  are  subject  to  many  bacterial  diseases,  and 
one  of  the  objects  of  thorough  cleaning  of  the  wheat 
and  removal  of  the  bran  and  debris  particles  during  the 
process  of  flour  manufacture  is  to  completely  eliminate 
all  ferment  bodies  mechanically  associated  with  the 
exterior  of  the  wheat  kernel,  which,  if  retained  in  the 
flour,  would  cause  it  readily  to  become  unsound. 

178.    Production    of    Soluble    Carbohydrates.  —  Floun 

contains  naturally  a  small  amount  of  soluble  carbohy-  ] 
drates,  which  are  readily  acted  upon  by  the  alcoholic 
ferments.  The  yeast  plant  secretes  soluble  ferments, 
which  act  upon  the  starch,  forming  soluble  carbohydrates, 
and  the  heat  during  baking  brings  about  similar  changes. 
In  fact,  soluble  carbohydrates  are  both  consumed  and 
produced  by  ferment  action  during  the  bread-making 
process.  Flour  contains,  on  an  average,  65  per  cent  of 
starch,  and  during  bread  making  about  10  per  cent  is 
changed  to  soluble  forms.  Bread,  on  a  dry  matter  basis, 
contains  approximately  6  per  cent  of  soluble  carbohy- 
drates, including  dextrine,  dextrose,  and  sucrose  sugars.64 


l66       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

The  physical  changes  which  the  starch  grains  undergo 
are  also  noticeable.  Wheat  starch  has  the  structure 
shown  in  illustration  No.  33.  The  starch  grains  are 
circular  bodies,  concave,  with  slight  markings  in  the 
form  of  concentric  rings.  When  the  proteid  matter  of 
bread  is  extracted  with  alcohol  and  the  starch  grains 
are  examined,  it  will  be  seen  that  some  of  them  are 
partially  ruptured,  like  those  in  popped  corn,  while 
others  have  been  slightly  acted  upon  or  eaten  away  by 
the  organized  ferments,  the  surface  of  the  starch  grains 
being  pitted,  as  shown  in  the  illustration.  The  joint 
action  of  heat  and  ferments  on  the  starch  grains  changes 
them  physically  so  they  may  more  readily  undergo 
digestion.  The  brown  coating  or  crust  formed  upon  the 
surface  of  bread  is  mainly  dextrine,  produced  by  the 
action  of  heat  on  the  starch.  Dextrine  is  a  soluble  car- 
bohydrate, having  the  same  general  composition  as 
starch,  but  differing  from  it  in  physical  properties  and 
ease  of  digestion. 

179.  Production  of  Acids  in  Bread  Making.  —  Wheat 
bread  made  with  yeast  gives  an  acid  reaction.  The 
acid  is  produced  from  the  carbohydrates  by  ferment 
action.  Flour  contains  about  one  tenth  of  I  per  cent 
of  acid;  the  dough  contains  from  0.3  to  0.5  per  cent, 
while  the  baked  bread  contains  from  o.  14  to  0.3  per  cent, 
but  after  two  or  three  days  slightly  more  acid  is  devel- 
oped.64 During  the  process  of  bread  making,  a  small 
portion  of  the  acid  is  volatilized,  but  the  larger  part 


BREAD    AND    BREAD    MAKING  167 

enters  into  chemical  combination  with  the  gliadin,  form- 
ing an  acid  proteid.  When  the  alcoholic  fermentation 
of  bread  making  becomes  less  active,  acid  fermentations 
begin,  and.  sour  dough  results.  It  is  not  definitely 
known  what  specific  organic  acids  are  developed  in 
bread  making.  Lactic  and  butyric  acids  are  known  to 
be  formed,  and  for  purposes  of  calculation,  the  total 
acidity  is  expressed  in  terms  of  lactic  acid. 

The  acidity  is  determined  by  weighing  20  grams  of 
flour  into  a  flask,  adding  200  cubic  centimeters  of 
distilled  water,  shaking  vigorously,  and  leaving  the 
flour  in  contact  with  the  water  for  an  hour;  50  cubic 
centimeters  of  the  filtered  solution  are  then  titrated  with  a 
tenth  normal  solution  of  potassium  hydroxid.  Phenol- 
phthalein  is  used  as  the  indicator.  It  cannot  be  said 
that  all  of  the  alkali  is  used  for  neutralizing  the  acid, 
as  a  portion  enters  into  chemical  combination  with  the 
proteids.  If  the  method  for  determining  the  acid  be 
varied,  constant  results  are  not  secured.  Unsound 
or  musty  flours  usually  show  a  high  per  cent  of  acidity. 

180.  Volatile  Compounds  produced  during  Bread  Mak- 
ing.—  In  addition  to  carbon  dioxid  and  alcohol,  there 
is  lost  during  bread  making  a  small  amount  of  carbon 
in  other  forms,  as  volatile  acicfs  and  hydrocarbon 
products  equivalent  to  about  one  tenth  of  one  per  cent 
of  carbon  dioxid.  The  aroma  of  freshly  baked  bread 
is  due  to  these  compounds.  Both  the  odor  and 
flavor  of  bread  are  caused  in  part  by  the  volatile  acids 


l68      HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 


and  hydrocarbons.  The  amount  and  kind  of  volatile 
products  formed  can  be  somewhat  regulated  through 
the  fermentation  process  by  the  use  of  special  flours 
and  the  addition  of  materials  that  produce  specific 
fermentation  changes  and  desirable  aromatic  com- 
pounds. Some  of  the  ferment  bodies  left  in  flour  from 


FIG.  48.  —  APPARATUS  USED  IN  STUDY  OF  LOSSES  IN  BREAD  MAKING. 

the  imperfect  removal  of  the  dirt  adhering  to  the  ex- 
terior of  the  wheat  kernels  impart  characteristic 
flavors  to  the  bread.  The  so-called  nutty  -flavor  of 
some  bread  is  due  to  the  action  of  these  ferment 
bodies  and,  when  intensified,  it  becomes  objectionable. 
Fungous  growths  in  unsound  flour  and  bread  result 
in  the  liberation  of  volatile  products,  which  impart  a 
musty  odor.  Good  odor  and  flavor  are  very  desirable 
in  both  flour  and  bread. 


"  BREAD    AND    BREAD    MAKING  169 

181.   Behavior  of  Wheat  Proteids  in  Bread  Making.  - 

Gluten  is  an  ingredient  of  the  flour  on  which  its  bread- \ 
making  properties  largely  depend.  The  important  I 
thing,  however,  is  not  entirely  the  quantity  of  gluten,  j 
but  more  particularly  its  character.  Two  flours  ] 
containing  the  same  amounts  of  carbohydrates  and 
proteid  compounds,  when  converted  into  bread  by 
exactly  the  same  process,  may  produce  bread  of  entirely 
different  physical  characteristics  because  of  differences 
in  the  nature  of  the  gluten  of  the  two  samples.  yGluten 
is  composed  of  two  bodies  called  gliadin  and  glutenin. 
The  gliadin,  a  sort  of  plant  gelatin,  is  the  material 
which  binds  the  flour  particles  together  to  form  the 
dough,  thus  giving  it  tenacity  and  adhesiveness ;  and 
the  glutenin  is  the  material  to  which  the  gliadin 
adheres.  If  there  is  an  excess  of  gliadin,  the  dough  is 
soft  and  sticky,  while  if  there  is  a  deficiency,  it  lacks 
expansive  power.  Many  flours  containing  a  large 
amount  of  gluten  and  total  proteid  material  and 
possessing  a  high  nutritive  value,  do  not  yield  bread 
of  the  best  quality,  because  of  an  imperfect  blending 
of  the  gliadin  and  glutenin.  This  question  is  of  much 
importance  in  the  milling  of  wheats,  especially  in  the 
blending  of  the  different  types  of  wheat.  An  abnor- 
mally large  amount  of  gluten  does  not  yield  a  corre- 
spondingly large  loaf. 

Experiments  were  made  at  the  Minnesota  Experiment 
Station  to  determine  the  relation  between  the  nature 
of  the  gluten  and  the  character  of  the  bread.  This  was 


170      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

done  by  comparing  bread  from  normal  flour  with 
that  from  other  flour  of  the  same  lot,  but  having  part 
or  all  of  its  gliadin  extracted.64  Dough  made  from  the 
latter  was  not  sticky,  but  felt  like  putty,  and  broke 


FIG.  49.  — BREAD  FROM  NORMAL  FLOUR  (i) ;  GLIADIN  EXTRACTED  FLOUR 
(2)  ;  AND  FROM  FLOUR  AFfER  EXTRACTION  OF  SUGAR  AND  SOLUBLE 
PROTEIDS  (3). 


in  the  same  way.  The  yeast  caused  the  mass  t* 
expand  a  little  when  first  placed  in  the  oven ;  then 
the  loaf  broke  apart  at  the  top  and  decreased  in  size. 
When  baked  it  was  less  than  half  the  size  of  that 
from  the  same  weight  of  normal  flour,  and  decidedly 
inferior  in  other  respects.  The  removal  of  part  of 


BREAD    AND    BREAD    MAKING  171 

the  gliadin  produced  nearly  the  same  effect  as  the 
extraction  of  the  whole  of  it,  and  even  when  an  equal 
quantity  of  normal  flour  was  mixed  with  that  from 
which  part  of  the  gliadin  had  been  extracted,  the 
bread  was  only  slightly  improved.  In  flour  of  the 
highest  bread-making  properties  the  two  constituents, 
gliadin  and  glutenin,  are  present  in  such  proportions 
as  to  form  a  well-balanced  gluten. 

The  proteids   of   wheat   flour  are   mainly  in   an   in- 
soluble  form,    although   there   are   small    an^punts    of 
albumins  and  globulins ;  these    are  coagulated    by  the 
action  of  heat  during    the  bread-making  process,  and 
rendered   insoluble.       A    portion    of   the    acid   that    is 
developed  unites  with  the  gliadin  and  glutenin,  forming 
acid   proteids,   which   change   the   physical    properties 
of   the  dough.       Both   gliadin   and    glutenin   take   im- 
portant parts  in  bread  making.     The  removal  of  gliadin 
from    flour     causes    complete    loss    of    bread-makin 
properties.       Ordinarily   from    45    to    65    per    cent    c 
the  total  nitrogen  of   the   flour   is   present   in  alcohc 
soluble    or   gliadin    form.     Proteids    also    undergo    h 
dration  during  mixing,    some   water   being   chemicall 
united  with  them,  changing  their  physical   properties^ 
This    hydration   change   is    necessary  for   the   full  de- 
velopment of   the   physical   properties   of   the   gluten. 
The  water   and   salt   soluble    proteids   appear   to   take 
no    important    part   in    the    bread-making    process,    as 
their  removal  in   no  way  affects   the   size  of  the  loaf 
or  general   character    of   the   bread.     Because   of   the 


172        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

action  of  the  acids  upon  the  gliadin,  bread  contains 
a  larger  amount  of  alcohol  soluble  nitrogen  or  gliadin 
than  the  flour  from  which  the  bread  was  made.  It 
is  believed  that  this  action  changes  the  molecular 
structure  of  the  protein  so  that  it  is  more  readily 
separated  into  its  component  parts  when  it  undergoes 
digestion  and  assimilation. 

182.   Production  of  Volatile   Nitrogenous   Compounds. 

-  When  fermentation  is  unnecessarily  prolonged,  an 
appreciable  amount  of  nitrogen  is  volatilized  in  the 
form  of  ammonia  and  allied  bodies,  as  amids.  During 
the  process  of  bread  making,  the  yeast  appears  to  act 
upon  the  protein,  as  well  as  upon  the  carbohydrates, 
and,  as  previously  stated,  losses  of  dry  matter  fall 
alike  upon  these  two  classes  of  compounds,  nitrogenous 
and  non-nitrogenous.  Analyses  of  the  flours  and 
materials  used  in  bread  making,  and  of  the  bread,  show 
that  ordinarily  about  1.5  per  cent  of  the  total  nitrogen 
is  liberated  in  the  form  of  gas  during  the  bread-mak- 
ing process,  and  analyses  of  the  gases  dispelled  in 
baking  show  approximately  the  same  per  cent  of 
nitrogen.  When  bread  is  dried,  as  in  a  drying  oven, 
a  small  amount  of  volatile  nitrogen  appears  to  be 
given  off,  —  probably  as  ammonium  compounds  formed 
during  fermentation.  The  nitrogen  lost  in  bread  mak- 
ing under  ordinary  conditions  is  not  sufficient  to  affect 
the  nutritive  value  of  the  product.  The  losses  of  both 
nitrogen  and  carbon  are  more  than  offset  by  the  in- 


BREAD    AND    BREAD    MAKING  173 

creased  solubility  of  the  proteids  and  carbohydrates, 
the  preliminary  changes  they  have  undergone  making 
them  more  digestible  and  valuable  for  food  purposes. 
The  nitrogen  volatilized  in  bread  making  appears  to 
be  mainly  that  present  in  the  flour  in  amid  forms  or 
liberated  as  the  result  of  fermentation  processes.  The 
more  stable  proteids  undergo  only  limited  changes  in 
solubility  and  are  not  volatilized. 

183.  Oxidation   of   Fat.  —  Flour   contains  about  1.25 
per  cent  of  fat  mechanically  mixed  with  a  small  amount 
of  yellow  coloring  matter.     During  the  process  of  bread 
making  the  fat  undergoes  slight  oxidation,  accompanied 
by  changes   in  both  physical  and  chemical  properties. 
The  fat  from  bread,  when  no  lard  or  shortening  has  been 
added,  is  darker  in  color,  more  viscous,  less  soluble  in 
ether,  and  has  a  lower  iodine   number,  than  fat  from 
flour.     The  change  in  solubility  of  the  fat  is  not,  how- 
ever, such  as  to  affect  food  value,  because  the  fat  is  not 
volatilized,    and  is  only  changed  by  the  addition  of  a 
small  amount  of  oxygen  from  the  air.     When  wheat  fat 
and  other  vegetable  and  animal  fats  are  exposed  to  the 
air,  they  undergo  changes  known  as  aging,  similar  to 
the  slight  oxidation  changes  in  bread  making.64 

184.  Influence  of  the  Addition  of  Wheat  Starch  and 
Gluten  to  Flour. — Ten  per  cent  or  more  of  starch  may 
be  added  to  normal   flour    containing   a   well-balanced 
gluten,  without  decreasing  the  size  of  the  loaf.     When 
moist   gluten   was  added  to  flour,  thus  increasing   the 


174        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

total  amount  of   gluten,  the  size  of   the  loaf   was  not 
increased.67 

INFLUENCE  OF  ADDITION  OF  STARCH  AND  GLUTEN  TO  FLOUR 


SIZE  OF  LOAF 

WEIGHT 

Wheat  flour,  14  ounces  

22i   X    \*J\ 

18  yc; 

Wheat  flour,  10  %  wheat  starch  .... 
Wheat  flour,  12.2  %  wheat  starch  .  .  .  . 

23i  x  17 

21  1   X    I/ 

18.25 
18.00 

Wheat  flour,  210  grams,  about  8  ounces  .  . 
Wheat  flour,  10  %  gluten  added,  210  grams  . 
Wheat  flour,  20  %  gluten  added  .... 

12}  X  9 
I2J  X  9 
12      X  8} 

I2.OO 
12.75 
I3.OO 

So  long  as  the  quality  of  the  gluten  is  not  destroyed, 
the  addition  of  a  small  amount  of  either  starch  or  gluten 
to  flour  does  not  affect  the  size  of  the  loaf,  but  removal 
of  the  gluten  affects  the  moisture  content  and  physical 
properties  of  the  bread.  The  addition  of  starch  to  flour 
has  the  same  effect  upon  the  bread  as  the  use  of  low 
gluten  flour, — lessening  the  capacity  of  the  flour  to 
absorb  water  and  producing  a  dryer  bread  of  poorer 
quality. 

185.  Composition  of  Bread.  — The  composition  of  bread 
depends  primarily  upon  that  of  the  flour  from  which  it 
was  made.  If  milk  and  butter  (or  lard)  are  used  in  mak- 
ing the  dough,  as  is  commonly  the  case,  their  nutrients 
are,  of  course,  added  to  those  of  the  flour;  but  when 
only  water  and  flour  are  used,  the  nutrients  of  the  bread 


BREAD  AND  BREAD  MAKING  175 

are  simply  those  of  the  flour.  In  either  case  the  amount 
of  nutrients  in  the  bread  is  smaller  than  in  the  same 
weight  of  flour,  because  a  considerable  part  of  the 
water  or  milk  used  in  making  the  dough  is  present  in  the 
bread  after  baking  ;  that  is,  a  pound  of  bread  contains  less 
of  any  of  the  nutrients  than  a  pound  of  the  flour  from 
which  the  bread  was  made,  because  the  proportion  of 
water  in  the  bread  is  greater.  The  following  table  shows 
how  the  composition  of  flour  compares  with  that  of  bread, 
the  different  kinds  of  bread  all  having  been  made  from 
the  flour  with  which  they  are  compared  : 


COMPOSITION  OF  FLOUR,  AND  BREAD  MADE  FROM  IT  IN 
DIFFERENT  WAYS 


MATERIAL 

WATER 

PROTEIN 

FAT 

C.H. 

ASH 

Flouc_ 

IO.I  I 

12.47 

0.86 

76.OQ 

O.A.7 

Bread  from  flour  and  water    .     . 

36.12 

9.46 

0.40 

53.70 

0.32 

Bread  from  flour,,  .water.'  and  lard 

37.70 

9.27 

1.02 

5*  -7° 

0.31 

Bread  from  flour  and  skim  milk 

36.02 

10.57 

0.48 

52.63 

0.30 

Thus  it  may  be  seen  that  the  proportion  of  water  is 
larger  and  of  each  nutrient  smaller  in  bread  than  in 
flour,  and  that  the  nutrients  of  the  flour  are  in- 
creased by  those  in  the  materials  added  in  making  the 
bread. 

It  is  apparent  that  two  breads  of  the  same  lot  of  flour 
may  differ,  according  to  the  method  used  in  making, 


176      HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

and  also  that  two  loaves  of  bread  made  by  exactly  the 
same  process  but  from  different  lots  of  flour,  even  when 
of  the  same  grade  or  brand,  do  not  necessarily  have  the 
same  composition,  because  of  possible  variation  in  the 
flours.  In  bread  made  from  flour  of  low  gluten  content, 
the  per  cent  of  protein  is  correspondingly  low. 

186.  Use  of  Skim  Milk  and  Lard  in  Bread  Making.  - 

When  flours  low  in  gluten  are  used,  skim  milk  may  be 
employed  advantageously  in  making  the  bread,  to  increase 
the  protein  content.  Tests  show  that  such  bread  contains 
about  i  per  cent  more  protein  than  that  made  with 
water.  Ordinarily  there  is  no  gain  from  a  nutritive 
point  of  view  in  adding  an  excessive  amount  of  lard  or 
other  shortening,  as  it  tends  to  widen  the  nutritive 
ratio. 

187.  Influence  of  Warm   and  Cold   Flours   on  Bread 
Making. — rWhen  flour  is  stored  in  a  cold  closet  or  store- 
room, it  is  not  in  condition  to  produce  a  good  quality  of 
bread  until  it  has  been  warmed  to  a  temperature  of  about 
70°  F.     Cold  flour  checks  the  fermentation  process,  and 
is  occasionally  the  cause  of  poor  bread.     On  the  other 
hand,  when  flour  is  too  warm  (98°  F.)  the  influence  upon 
fermentation  is  unfavorable.     Heating  of  flour  does  not 
affect  the  bread-making  value,  provided  the  flour  is  not 
heated  above   158°  F.  and  is  subsequently  cooled  to  a 

i  temperature  of  70°.     Wheat  flour  contains  naturally  a 
Inumber  of  ferment  substances,  some  of  which  are  de- 


BREAD   AND    BREAD    MAKING 


177 


stroyed  by  the  action  of  heat.  The  natural  ferments,  or 
enzymes,  of  flour  appear  to  take  a  part  in  bread  making, 
imparting  characteristic  odors  and  flavors  to  the  prod- 
uct. 

188.   Variations  in  the  Process  of  Bread  Making. — 

Since  flours  differ  so  in  chemical  composition,  and  the 


I  2  3 

FIG.  50.  — BREAD  FROM  (i)  GRAHAM,  (2)  ENTIRE  WHEAT,  AND 
(3)  WHITE  FLOUR. 

The  same  amounts  of  flour  were  used  in  making  all  of  the  breads. 


yeast  plant  acts  upon  all  the  compounds  of  flour,  it  natu- 
rally follows  that  bread  making  is  not  a  simple  but  a 
complex  operation,  resulting  in  a  number  of  intricate 
chemical  reactions,  which  it  is  necessary  to  control  and 
many  of  which  are  only  imperfectly  understood.  Bread 


178      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

of  the  best  physical  quality  and  commercial  value  is 
made  of  flour  from  fully  matured,  hard  wheats,  contain- 
ing a  low  per  cent  of  acid,  no  foreign  ferment  materials 
or  their  products,  and  at  least  \2\  per  cent  of  pro- 
teids,  of  which  the  larger  portion  is  in  the  form  of 
gliadin.  It  is  believed  that  a  better  quality  of  bread 
could  be  produced  from  many  flours  by  slight  changes 
or  modifications  in  the  process  of  bread  making.  It  can- 
not be  expected  that  the  same  process  will  give  the  best 
results  alike  with  all  types  and  kinds  of  flour.  The  kind 
of  fermentation  process  that  will  produce  the  best  bread 
from  a  given  type  of  flour  can  be  determined  only  by 
experimentation.  Poor  bread  making  is  due  as  often  to 
lack  of  skill  on  the  part  of  the  bread  maker,  and  to  poor 
yeast,  as  it  is  to  poor  quality  of  flour.  Frequently  the 
flour  is  blamed  when  the  poor  bread  is  due  to  other  fac- 
tors. Lack  of  control  of  the  fermentation  process,  and 
the  consequent  development  of  acid  and  other  organisms 
which  check  the  activity  of  the  alcoholic  ferments,  is  a 
frequent  cause  of  poor  bread. 

189.  Digestibility  of  Bread.  —  Extensive  experiments 
have  been  made  by  the  Office  of  Experiment  Stations  of 
the  United  States  Department  of  Agriculture,  at  the 
Minnesota  and  Maine  Experiment  Stations,  to  determine 
the  digestibility  and  nutritive  value  of  bread.  Different 
kinds  and  types  of  wheat  were  milled  so  as  to  secure 
from  each  three  flours  :  graham,  entire  wheat,  and  stand- 
ard patent.  The  flours  were  made  into  bread,  and  the 


BREAD   AND    BREAD   MAKING  179 

bread  fed  to  workingmen,  and  its  digestibility  deter- 
mined. The  experiments  taken  as  a  whole  show  that 
bread  is  an  exceedingly  digestible  food,  nearly  98  per 
cent  of  the  starch  or  carbohydrate  nutrients  and  about 
88  per  cent  of  the  gluten  or  proteid  constituents  being 
assimilated  by  the  body.  /  In  the  case  of  the  graham  and 
entire  wheat  flours,  although  they  contained  a  larger 
total  amount  of  protein,  the  nutrients  were  not  as  com- 
pletely digested  and  absorbed  by  the  body  as  were  those 
of  the  white  flour.  *  The  body  secured  a  larger  amount 
of  nutrients  from  the  white  than  from  the  other  grades 
of  flour,  the  digestibility  of  the  three  types  being  as  fol- 
lows :  standard  patent  flour,  protein  88.6*  per  cent  and 
carbohydrates  97.7  per  cent;  entire  wheat  flour,  protein 
82  per  cent  and  carbohydrates  93.5  per  cent;  graham 
flour,  protein  74.9  per  cent  and  carbohydrates  89.2  per 
cent.  The  low  digestibility  of  the  protein  of  the  graham 
and  entire  wheat  flours  is  supposed  to  be  due  to  the 
coarser  granulation ;  the  proteins,  being  embedded  and 
surrounded  with  cellular  tissue,  escape  the  action  of  the 
digestive  fluids.  Microscopic  examination  of  the  feces 
showed  that  often  entire  starch  grains  were  still  inclosed 
in  the  woody  coverings  and  consequently  had  failed  to 
undergo  digestion.62'64'67'86 

190.   Use  of  Graham  and  Entire  Wheat  in  the  Dietary. 

—  Entire  wheat  and  graham  flours  should  be  included 
in  the  dietary  of  some  persons,  as  they  are  often  valu- 
able because  of  their  physiological  action,  the  branny 


l8o       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

particles  stimulating  the  process  of  digestion  and  en- 
couraging peristaltic  action.  In  the  diet  of  the  overfed, 
they  are  valuable  for  the  smaller  rather  than  the  larger 
amount  of  nutrients  they  contain.  Also  they  supply 
bulk  and  give  the  digestive  tract  needed  exercise.  For 
the  laboring  man,  where  it  is  necessary  to  obtain  the 
largest  amount  of  available  nutrients,  bread  from  white 
flour  should  be  supplied ;  in  the  dietary  of  the  sedentary, 
graham  and  entire  wheat  flours  can,  if  found  beneficial, 
be  made  to  form  an  essential  part.  The  kind  of  bread 
that  it  is  best  to  use  is  largely  a  matter  of  personal  choice 
founded  upon  experience. 

"  When  we  pass  on  to  consider  the  relative  nutritive  values  of 
white  and  whole-meal  bread,  we  are  on  ground  that  has  been  the 
scene  of  many  a  controversy.  It  is  often  contended  that  whole-meal 
is  preferable  to  white  bread,  because  it  is  richer  in  proteid  and 
mineral  matter,  and  so  makes  a  better  balanced  diet.  But  our  ex- 
amination of  the  chemical  composition  of  whole-meal  bread  has  shown 
that  as  regards  proteid  at  least,  this  is  not  always  true,  and  even 
were  it  the  case,  the  lesser  absorption  of  whole-meal  bread,  which  we 
have  seen  to  occur,  would  tend  to  annul  the  advantage.  .  .  .  On  the 
whole,  we  may  fairly  regard  the  vexed  question  of  whole-meal  versus 
white  bread  as  finally  settled  and  settled  in  favor  of  the  latter."  28 

"  The  higher  percentage  of  nitrogen  in  bran  than  in  fine  flour  has 
frequently  led  to  the  recommendation  of  the  coarser  breads  as  more 
nutritious  than  the  finer.  We  have  already  seen  that  the  more 
branny  portions  of  the  grain  also  contain  a  much  larger  percentage 
of  mineral  matter.  And,  further,  it  is  in  the  bran  that  the  largest 
proportion  of  fatty  matter  —  the  non-nitrogenous  substance  of  higher 
respiratory  capacity  which  the  wheat  contains — is  found.  It  is, 
however,  we  think,  very  questionable  whether  upon  such  data  alone 


BREAD   AND  BREAD   MAKING  l8l 

a  valid  opinion  can  be  formed  of  the  comparative  values  of  bread 
made  from  the  finer  or  coarser  flours  ground  from  one  and  the  same 
grain.  Again,  it  is  an  indisputable  fact  that  branny  particles  when 
admitted  into  the  flour  in  the  degree  of  imperfect  division  in  which 
our  ordinary  milling  processes  leave  them  very  considerably  increase 
the  peristaltic  action,  and  hence  the  alimentary  canal  is  cleared  much 
more  rapidly  of  its  contents.  It  is  also  well  known  that  the  poorer 
classes  almost  invariably  prefer  the  whiter  bread,  and  among  some 
of  those  who  work  the  hardest  and  who  consequently  soonest  appre- 
ciate a  difference  in  nutritive  quality  (navvies,  for  example)  it  is 
distinctly  stated  that  their  preference  for  the  whiter  bread  is  founded 
on  the  fact  that  the  browner  passes  through  them  too  rapidly ;  con- 
sequently, before  their  systems  have  extracted  from  it  as  much 
nutritious  matter  as  it  ought  to  yield  them.  ...  In  fact,  all  experi- 
ence tends  to  show  that  the  state  as  well  as  the  chemical  composi- 
tion of  our  food  must  be  considered ;  in  other  words,  that  the 
digestibility  and  aptitude  for  assimilation  are  not  less  important 
qualities  than  its  ultimate  composition. 

"  But  to  suppose  that  whole-wheat  meal  as  ordinarily  prepared  is, 
as  has  generally  been  assumed,  weight  for  weight  more  nutritious 
than  ordinary  bread  flour  is  an  utter  fallacy  founded  on  theoretical 
text-book  dicta,  not  only  entirely  unsupported  by  experience,  but  in- 
consistent with  it.  In  fact,  it  is  just  the  poorer  fed  and  the  harder 
working  that  should  have  the  ordinary  flour  bread  rather  than  the 
whole-meal  bread  as  hitherto  prepared,  and  it  is  the  overfed  and 
the  sedentary  that  should  have  such  whole-meal  bread.  Lastly,  if  the 
whole  grain  were  finely  ground,  it  is  by  no  means  certain  that  the 
percentage  of  really  nutritive  nitrogenous  matters  would  be  higher 
than  in  ordinary  bread  flour,  and  it  is  quite  a  question  whether 
the  excess  of  earthy  phosphates  would  not  then  be  injurious." 

—  LAWES  AND   GILBERT.68 

"  According  to  the  chemical  analysis  of  graham,  entire  wheat,  and 
standard  patent  flours  milled  from  the  same  lot  of  hard  Scotch  Fife 
spring  wheat,  the  graham  flour  contained  the  highest  and  the  patent 


1 82       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

flour  the  lowest  percentage  of  total  protein.  But  according  to  the 
results  of  digestion  experiments  with  these  flours  the  proportions  of 
digestible  or  available  protein  and  available  energy  in  the  patent  flour 
were  larger  than  in  either  the  entire  wheat  or  the  graham  flour.  The 
lower  digestibility  of  the  protein  of  the  latter  is  due  to  the  fact  that 
in  both  these  flours  a  considerable  portion  of  this  constituent  is  con- 
tained in  the  coarser  particles  (bran),  and  so  resists  the  action  of  the 
digestive  juices  and  escapes  digestion.  Thus  while  there  actually 
may  be  more  protein  in  a  given  amount  of  graham  or  entire  wheat: 
flour  than  in  the  same  weight  of  patent  flour  from  the  same  wheat, 
the  body  obtains  less  of  the  protein  and  energy  from  the  coarse  flour 
than  it  does  from  the  fine,  because,  although  the  including  of  the 
bran  and  germ  increases  the  percentage  of  protein,  it  decreases  its 
digestibility.  By  digestibility  is  meant  the  difference  between  the 
amounts  of  the  several  nutrients  consumed  and  the  amount  excreted 
in  the  feces. 

"  The  digestibility  of  first  and  second  patent  flours  was  not  appre- 
ciably different  from  that  of  standard  patent  flour.  The  degree 
of  digestibility  of  all  these  flours  is  high,  due  largely  to  their  mechan- 
ical condition  ;  that  is,  to  the  fact  that  they  are  finely  ground."  — 

SNYDER.62 

For  a  more  extended  discussion  of  the  subject,  the 
student  is  referred  to  Bulletins  67,  101,  and  126,  Office 
of  Experiment  Stations,  United  States  Department  of 
Agriculture. 

191.  Mineral  Content  of  White  Bread.  —  Average  flour 
contains  from  0.4  to  0.5  of  I  per  cent  of  ash  or  mineral 
matter,  the  larger  portion  being  lime  and  magnesia  and 
phosphate  of  potassium.  It  is  argued  by  some  that 
graham  and  entire  wheat  flours  should  be  used  liberally 
because  of  their  larger  mineral  content  and  their  greater 


BREAD   AND    BREAD    MAKING  183 

richness  in  phosphates.  In  a  mixed  Apiary,  however, 
in  which  bread  forms  an  essential  part,  there  is  always 
an  excess  of  phosphates,  and  there  is  nothing  to  be  gained 
by  increasing  the  affiount,  as  it  only  requires  additional 
work  of  the  kidneys  for  its  removal.  Few  experiments 
have  been  made  to  determine  the  phosphorus  require- 
ments of  the  human  body,  but  these  indicate  that  it  is 
unnecessary  to  increase  the  phosphate  content  of  a 
mixed  diet.  It  is  estimated  that  less  than  two  grams  per 
day  of  phosphates  are  required  to  meet  all  of  the  needs 
of  the  body,  and  in  an  average  mixed  ration  there  are 
present  from  three  to  five  grams  and  more.  A  large 
portion  of  the  phosphate  compounds  of  white  bread  is 
present  in  organic  combinations,  as  lecithin  and  nucleated 
proteids,  which  are  the  most  available  forms,  and  more 
valuable  for  purposes  of  nutrition  than  the  mineral 
phosphates.  In  the  case  of  graham  and  entire  wheat 
flours,  a  proportionally  smaller  amount  of  the  phos- 
phates are  digested  and  assimilated  than  from  the  finer 
grades  of  flour. 

192.   Comparative  Digestibility  of  New  and  Old  Bread. 

—  With  healthy  persons  there  is  no  difference  whatever 
in  the  completeness  of  digestibility  of  old  and  new 
bread ;  one  appears  to  be  as  thoroughly  absorbed  as  the 
other.  In  the  case  of  some  individuals  with  impaired 
digestion  there  may  be  a  difference  in  the  ease  and  com- 
fort with  which  the  two  kinds  of  bread  are  digested,  but 
this  is  due  mainly  to  individuality  and  does  not  apply 


184       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

generally.  The  change  which  bread  undergoes  when  it 
is  kept  for  several  days  is  largely  a  loss  of  moisture  and 
development  of  a  small  amount  of  acid  and  other  sub- 
stances from  the  continued  ferment  action. 

193.  Different  Kinds  of  Bread.  —  According  to  varia- 
tions in  method  of  preparation,  there  are  different  types 
and  varieties  of  bread,  as  the  "  flat  bread  "  of  Scandi- 
navian countries,  unleavened  bread,  Vienna  bread,  salt 
rising   bread,    etc.     Bread    made  with   baking   powder 
differs  in  no  essential  way  from  that  made  with  yeast, 
except  in  the  presence  of  the  residue  from  the  baking 
powder,   discussed   in   Chapter   XII.     Biscuits,    wheat 
cakes,  crackers,  and  other  food  materials  made  princi- 
pally from  flour,  have  practically  the  same  food  value  as 
bread.     It  makes  but  little  difference  in  what  way  flour 
is  prepared  as  food,  for   in   its   various   forms   it   has 
practically  the  same  digestibility  and  nutritive  value. 

194.  Toast. — When   bread   is   toasted    there   is   no 
change   in  the  percentage  of  total   nutrients  on  a  dry 
matter  basis.     The  change  is  in  solubility  and  form,  and 
not  in  amount  of  nutrients  available.     Some  of  the  starch 
becomes  dextrine,  which  is  more  soluble  and  digestible.5 
Proteids,  on  the  other  hand,  are  rendered  less  soluble, 
which  appears  to  slightly  lower  the  digestion  coefficient. 
They  are  somewhat  more  readily  but  not  quite  so  com- 
pletely digested  as  those  of  bread.     Digestion  experi- 
ments show  that  toast  more  readily  yields  to  the  diastase 
and  other  ferments  than  does  wheat  bread.     Toasting 


BREAD  AND  BREAD  MAKING  185 

brings  about  ease  of  digestion  rather  than  increased 
completeness  of  the  process.  Toast  is  a  sterile  food, 
while  bread  often  contains  various  ferments  which  have 
not  been  destroyed  by  baking.  These  undergo  incuba- 
tion during  the  process  of  digestion,  particularly  in  the 
case  of  individuals  with  diseases  of  the  digestive  tract. 
With  normal  digestion,  however,  these  ferment  bodies 
do  not  develop  to  any  appreciable  extent,  as  the  digestive 
tract  disinfects  itself.  When  the  flour  is  prepared  from 
well  cleaned  wheat  and  the  ferment  substances  which 
are  present  mainly  in  the  bran  particles  have  been  re- 
moved, a  flour  of  higher  sanitary  value  is  secured. 


CHAPTER   XII 
BAKING  POWDERS 

195.  General  Composition.  —  All  baking  powders  con- 
tain at  least  two  materials ;  one  of  these  has  combined 
carbon  dioxid  in  its  composition,  the  other  some  acid 
constituent  which  serves  to  liberate  the  gas.  The  ma- 
terial from  which  the  gas  is  obtained  is  almost  invaria- 
bly sodium  bicarbonate,  NaHCO3,  commonly  known  as 
"  soda  "  or  "  saleratus."  Ammonium  carbonate  has  been 
used  to  some  extent,  but  is  very  seldom  used  at  the 
present  time.  The  acid  constituent  may  be  one  of  sev- 
eral materials,  the  most  common  being  cream  of  tartar, 
tartaric  acid,  calcium  phosphate,  or  alum.  These  may  be 
used  separately  or  in  combination.  The  various  baking 
powders  are  designated  according  to  the  acid  constituent, 
as  "cream  of  tartar,"  "phosphate,"  and  "alum  "  powders. 
All  of  them  liberate  carbon  dioxid  gas,  but  the  products 
left  in  the  food  differ  widely  in  nature  and  amount.69 

Baking  powder  is  a  chemical  preparation  which, 
when  brought  in  contact  with  water,  liberates  carbon 
dioxid  gas.  The  baking  powder  is  mixed  dry  with 
flour,  and  when  this  is  moistened  the  carbon  dioxid 
that  is  liberated  expands  the  dough.  The  action  is  simi- 

186 


BAKING    POWDERS  187 

lar  to  that  of  yeast  except  that  in  the  case  of  yeast  the 
gas  is  given  off  much  more  slowly  and  no  residue  is  left 
in  the  bread.  When  baking  powder  is  used,  there  is  a 
residue  left  in  the  food  which  varies  with  the  material 
in  the  powder.  It  is  the  nature  and  amount  of  this  resi- 


1234 

FIG.  51.  — INGREDIENTS  OF  A  BAKING  POWDER. 

I,  baking  powder;  2,  cream  of  tartar;  3,  baking  soda;  4,  starch. 

due  that  is  important  and  makes  one  baking    powder 
more  desirable  than  another. 

196.  Cream  of  Tartar  Powders.  —  The  acid  ingredient 
of  the  cream  of  tartar  powders  is  tartaric  acid,  H2C4H4O6. 
Cream  of  tartar  is  potassium  acid  tartrate,  KHC4H4O6 ; 
it  contains  one  atom  of  replaceable  hydrogen,  which  im- 
parts the  acid  properties,  and  it  is  prepared  from  crude 


1 88      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

argol,  a  deposit  of  grape  juice  when  wine  is  made.  The 
residue  from  this  powder  is  sodium  potassium  tartrate, 
NaKC4H4O6,  commonly  known  as  Rochelle  salt.  This 
is  the  active  ingredient  of  Seidlitz  powders  and  has  a 
purgative  effect  when  taken  into  the  body.  The  dose 
as  a  purgative  is  from  one  half  to  one  ounce.  A  loaf  of 
bread  as  ordinarily  made  with  cream  of  tartar  powder 
contains  about  160  grains  of  Rochelle  salt,  which  is  45 
grains  more  than  is  found  in  a  Seidlitz  powder,  but  the 
amount  actually  eaten  at  any  one  time  is  small  and  its 
physiological  effect  can  probably  be  disregarded.  When 
a  cream  of  tartar  baking  powder  is  used,  the  reaction 
takes  place  according  to  the  following  equation : 

HKH4C406  +  NaHC08  =  KNaC4°H4O6  +  CO2  +  H2Q, 

The  crystallized  Rochelle  salt  contains  four  molecules 
of  water,  so  that,  even  allowing  for  some  starch  filler, 
there  is  very  nearly  as  much  weight  of  material  (Ro- 
chelle salt)  left  in  the  food  as  there  was  of  the  original 
powder.  If  free  tartaric  acid  were  used  instead  of 
potassium  acid  tartrate,  the  reaction  would  be  as  follows  : 

H2C4H4O6  +  2  NaHC03  =  Na^H^  -  2  H2O  +  2  CO2. 

But  trie  residue,  sodium  tartrate,  is  less  in  proportion. 
It  has  physiological  properties  very  similar  to  Rochelle 
salt.  Tartaric  acid  is  seldom  used  alone,  but  very  often 
in  combination  with  cream  of  tartar.  It  is  more  expen- 
sive than  cream  of  tartar ;  but  not  so  much  is  required, 
and  it  is  more  rapid  in  action. 


BAKING    POWDERS  189 

197.  Phosphate    Baking    Powders.  —  Here   the   acid 
ingredient  is  phosphoric  acid  and  the  compound  usually 
employed    is    mono-calcium    phosphate,    CaH4  (PO4)2. 
This*  is  made  by  the  action  of  sulphuric  acid  on  ground 
bone  (Ca3(PO4)2  +  2  H2SO4  =  CaH4(PO4)2  +  2  CaSO4), 
and  it  is  difficult  to  free  it  from  the  calcium  phosphate 
formed  at  the  same  time;  hence  such  powders  contain 
more  or  less  of  this  inert  material.     The  reaction  which 
occurs  with  a  phosphate  powder  is  as  follows :  , 

234  168  136 

CaH4(PO4)2  +  2  NaHCO3  =  CaHPO4 

88  36  142 

+  2  CO2  +  2  H2O  +  Na2HPO4. 

Sodium  phosphate,  according  to  the  United  States 
Dispensatory,  is  "  mildly  purgative  in  doses  of  from  I 
to  2  ounces."  The  claim  is  made  by  the  makers  of 
phosphate  baking  powders  that  the  phosphates  of  so- 
dium and  calcium,  products  left  after  the  baking,  re- 
store the  phosphates  which  have  been  lost  from  the 
flour  in  the  bran.  This  baking  powder  residue  does 
not  restore  the  phosphates  in  the  same  form  in  which 
they  are  present  in  grains  and  it  does  furnish  them  in 
larger  amounts  —  nearly  tenfold.  However,  the  resi- 
due from  these  powders  is  probably  less  objectionable 
than  that  from  alum  powders.  The  chief  drawback  to 
the  phosphate  powders  is  their  poor  keeping  qualities. 

198.  Alum  Baking  Powders.  —  Sulphuric  acid  is  the 
acid  constituent  of  these  powders.     The  alums  are  double 


1 90      HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

sulphates  of  aluminium  and  an  alkali  metal,  and  have  the 
general  formula  ^A1(SO4)2  in  which  x  may  be  K,  Na, 
or  NH4,  producing  respectively  a  potash,  soda,  or 
ammonia  alum.  Potash  alum  is  most  commonly  used, 
soda  and  ammonia  alums  to  a  less  extent.  The  reac- 
tion takes  place  as  follows  : 

475  504  157 

^NH4A1(SO4)2  +  6  NaHCO3  =  A12(OH)6 

+  3  Na2S04  +  (NH4)2SO4  +6  CO2. 

If  it  is  a  potash  or  soda  alum,  simply  substitute  K  or 
Na  for  NH4  throughout  the  equation.  The  best  authori- 
ties regard  alum  baking  powders  as  the  most  objection- 
able. Ammonia  alum  is  without  doubt  the  worst  form, 
since  all  of  the  ammonium  compounds  have  an  ex- 
tremely irritating  effect  on  animal  tissue.  Sulphates  of 
sodium  and  potassium  are  also  objectionable.  Alumin- 
ium hydroxide  is  soluble  in  the  slightly  acid  gastric  juice 
and  has  an  astringent  action  on  animal  tissue,  hindering 
digestion  in  a  way  similar  to  the  alum  itself.  Many 
of  the  alum  powders  contain  also  monocalcium  phos- 
phate ;  the  reaction  is  as  follows : 

475  234  336 

2  NH4A1(SO4)2  +  CaH4(PO4)2  +  4  NaHCO3 
=  A12(PO4)2       +  CaSO4  +  (NH4)2SO4 

284  176  72 

+  2Na2SO4        +4CO2  +4H2O. 

These  are  probably  less  injurious  than  the  straight 


BAKING    POWDERS  IQI 

alum  powders,  although  the  residues  are,  in  general, 
open  to  the  same  objection. 

199.  Inspection  of  Baking  Powders.  —  Many  of  the 
states  have  enacted  laws  seeking  to  regulate  the  sale  of 
alum  baking  powders.     Some  of  these  laws  simply  re- 
quire the  packages  to  bear  a  label  setting  forth  the  fact 
that  alum  is  one  of  the  ingredients ;  others  require  the 
baking  powder  packages  to  bear  a  label  naming  all  the 
ingredients  of  the  powder. 

200.  Fillers.  —  All  baking  powders  contain  a  filler  of 
starch.     This  is  necessary  to  keep  the  materials  from 
acting  before  the  powder  is  used.     The  amount  of  filler 
varies  from  15  to  50  per  cent ;  the  least  is  found  in  the 
tartrate  powders  and  the  most  in  the  phosphate  powders. 
The  amount  of  gas  which  a  powder  gives  off  regulates 
its  value ;  it  should  give  off  at  least  |-  of  its  weight. 

201.  Home-made  Baking  Powders.  —  Baking  powders 
can  be  made  at  home  for  about  one  half  what  they  usu- 
ally cost  and  they  will  give  equal  satisfaction.     The  fol- 
lowing will  make  a  long-keeping  powder  :  cream  of  tartar, 
8  ounces;  baking  soda,  4  ounces;  corn  starch,  3  ounces. 
For  a  quick- acting  powder  use  but  one  ounce  of  starch. 
The  materials  should  be  thoroughly  dry.     Mix  the  soda 
and    starch    first    by    shaking   well   in    a   glass   or   tin 
can.     Add  the  cream  of  tartar  last  and  shake  again. 
Thorough  mixing  is  essential  to  good  results.     Cream 


192       HUMAN   FOODS    AND   THEIR   NUTRITIVE    VALUE 

of  tartar  is  often  adulterated,  but  it  can  be  obtained 
pure  from  a  reliable  druggist.  To  insure  baking  pow- 
ders remaining  perfectly  dry,  they  should  always  be 
kept  in  glass  or  tin  cans,  never  in  paper. 


CHAPTER   XIII 
VINEGAR,  SPICES,  AND  CONDIMENTS 

202.  Vinegar.  —  Vinegar  is  a  dilute  solution  of  acetic 
acid  produced  by  fermentation,  and  contains,  in  addition 
to  acetic  acid,  small  amounts  of  other  materials  in  solution, 
as  mineral  matter  and  malic  acid,  according  to  the  ma- 
terial from  which  the  vinegar  was  made.  Unless  other 
wise  designated,  vinegar  in  this  country  is  generally 
considered  to  be  made  from  apples.  Other  substances, 
however,  are  used,  as  vinegar  can  be  manufactured  from 
a  variety  of  fermentable  materials,  as  molasses,  glucose, 
malt,  wine,  and  alcoholic  beverages  in  general.  The 
chemical  changes  which  take  place  in  the  production  of 
vinegars  are:  (i)  inversion  of  the  sugar,  (2)  conversion 
of  the  invert  sugars  into  alcohol,  and  (3)  change  of 
alcohol  into  acetic  acid.  All  these  chemical  changes 
are  the  result  of  ferment  action.  The  various  invert 
ferments  change  the  sugar  into  dextrose  and  glucose 
sugars ;  then  the  alcoholic  ferment  produces  alcohol  and 
carbon  dioxid  from  the  invert  sugars,  and  finally  the 
acetic  acid  ferment  completes  the  work  by  converting 
the  alcohol  into  acetic  acid.  The  chemical  changes 
which  take  place  in  these  different  steps  are : 
o  193 


IQ4      HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


(i)    C12H22On 


=  C6H12O6  4-  C6H12O6; 


dextrose  alcohol 

(2)     C6H1206  =  2  C2H5OH  +  2  C02  ; 


alcohol 

(3)    C2H5OH 


acid 

=  HC2H3O2  +  HO. 


FIG.  52.  — ACETIC  ACID  FERMENTS.    (After  KONIG.) 

The  acetic  acid  organism,  mycoderma  acti,  can  work 
only  in  the  presence  of  oxygen.  It  is  one  of  the  aerobic 
ferments,  and  is  present  in  what  is  known  as  the 
"mother"  of  vinegar  and  is  secreted  by  it.  When  vin- 
egar is  made  in  quantity,  the  process  is  hastened  by 


VINEGAR,    SPICES,    AND    CONDIMENTS  195 

allowing  the  alcoholic  solution  to  pass  through  a  narrow 
tank  filled  with  shavings  containing  some  of  the  ferment 
material,  and  at  the  same  time  air  is  admitted  so  as  to 
secure  a  good  supply  of  oxygen.  When  vinegar  is 
made  by  allowing  cider  or  wine  to  stand  in  a  warm 
place  until  the  fermentation  process  is  completed,  a  long 
time  is  required  —  the  length  of  time  depending  upon 
the  supply  of  air  and  other  conditions  affecting  fermen- 
tation. 

In  some  countries  malt  vinegar  is  common.  This  is 
produced  by  allowing  a  wort  made  from  malt  and  barley 
to  undergo  acetic  acid  fermentation,  without  first  dis- 
tilling the  alcohol  as  is  done  in  the  preparation  of  spirit 
vinegar.  In  various  European  countries  wine  vinegar 
is  in  general  use  and  is  made  by  acetification  of  the  juice 
of  grapes.  Sometimes  spirit  vinegar  is  made  from  corn 
or  barley  malt.  Alcoholic  fermentation  takes  place,  the 
alcohol  is  distilled  so  that  a  weak  solution  remains, 
which  is  acetified  in  the  ordinary  way.  Such  a  vinegar 
can  be  produced  very  cheaply  and  is  much  inferior  in 
flavor  to  genuine  wine  or  cider  vinegar. 

Vinegar,  when  properly  made,  should  remain  clear, 
and  should  not  form  a  heavy  deposit  or  produce  any 
large  amount  of  the  fungous  growth,  commonly  called 
the  "  mother  "  of  vinegar.  In  order  to  prevent  the  vine- 
gar from  becoming  cloudy  and  forming  deposits,  it  should 
be  strained  and  stored  in  clean  jugs  and  protected  from 
the  air.  So  long  as  air  is  excluded  further  acetic  acid 
fermentation  and  production  of  "  mother "  of  vinegar 


196       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

cannot  take  place.  When  the  vinegar  is  properly  made 
and  the  fermentation  process  has  been  completed,  the 
acid  already  produced  prevents  all  further  development 
of  acetic  acid  ferments.  When  vinegar  becomes  cloudy 
and  produces  deposits,  it  is  an  indication  that  the  acetic 
fermentation  has  not  been  completed. 

The  national  standard  for  pure  apple  cider  vinegar 
calls  for  not  less  than  4  grams  acetic  acid,  1.6  grams  of 
apple  solids,  and  0.25  grams  of  apple  ash  per  100  cubic 
centimeters,  along  with  other  characteristics,  as  acidity, 
sugar,  and  phosphoric  acid  content.  Many  states  have 
special  laws  regarding  the  sale  of  vinegar. 

203.  Adulteration  of  Vinegar.  —  Vinegar  is  frequently 
adulterated  by  the  addition  of  water,  or  by  coloring 
spirit  vinegar,  thus  causing  it  to  resemble  cider  vinegar. 
Formerly  vinegar  was  occasionally  adulterated  by  the  use 
of  mineral  acids,  as  hydrochloric  or  sulphuric,  but  since 
acetic  acid  can  be  produced  so  cheaply,  this  form  of 
adulteration  has  almost  entirely  disappeared.  Colored 
spirit  vinegar  contains  merely  a  trace  of  solid  matter 
and  can  be  readily  distinguished  from  cider  vinegar  by 
evaporating  a  small  weighed  quantity  to  dryness  and 
determining  the  weight  of  the  solids.  Occasionally,  how- 
ever, glucose  and  other  materials  are  added  so  as  to 
give  some  solids  to  the  spirit  vinegar,  but  such  a  vin- 
egar contains  only  a  trace  of  ash.18  Attempts  have  also 
been  made  to  carry  the  adulteration  still  further  by 
adding  lime  and  soda  to  give  the  colored  spirit  vin- 


VINEGAR,    SPICES,    AND    CONDIMENTS  1 97 

egar  the  necessary  amount  of  ash.  Malt,  white  wine, 
glucose,  and  molasses  vinegars  when  properly  manufac- 
tured and  unadulterated  are  not  objectionable,  but  too 
frequently  they  are  made  to  resemble  and  sell  as  cider 
vinegar.  This  is  a  fraud  which  affects  the  pocketbook 
rather  than  the  health.  For  home  use  apple  cider  vin- 
egar is  highly  desirable.  There  is  no  food  material 
or  food  adjunct,  unless  possibly  ground  coffee  and  spices, 
so  extensively  adulterated  as  vinegar. 

Vinegar  has  no  food  value  whatever,  and  is  valuable 
only  for  giving  flavor  and  palatability  to  other  foods, 
and  to  some  extent  for  the  preservation  of  foods.  It  is 
useful  in  the  household  in  other  ways,  as  it  furnishes  a 
dilute  acid  solution  of  aid  in  some  cooking  and  baking 
operations  for  liberating  gas  from  soda,  and  also  when 
a  dilute  acid  solution  is  required  for  various  cleaning 
purposes. 

Vinegar  should  never  be  kept  in  tin  pails,  or  any 
metallic  vessel,  because  the  acetic  acid  readily  dissolves 
copper,  tin,  iron,  and  the  ordinary  metals,  producing 
poisonous  solutions.  Earthenware  jugs,  porcelain  dishes, 
glassware,  or  wooden  casks  are  all  serviceable  for  storing 
vinegar. 

204.  Characteristics  of  Spices.70 —  Spices  are  aromatic 
vegetable  substances  characterized  as  a  class  by  contain- 
ing some  essential  or  volatile  oil  which  gives  taste  and 
individuality  to  the  material.  They  are  used  for  the 
flavoring  of  food  and  are  composed  of  mineral  matter 


198       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

and  the  various  nitrogenous  and  non-nitrogenous  com- 
pounds found  in  all  plant  bodies.  Since  only  a  com- 
paratively small  amount  of  a  spice  is  used  for  flavoring 
purposes,  no  appreciable  nutrients  are  added  to  the 
food.  Some  of  the  spices  have  characteristic  medicinal 
properties.  Occasionally  they  are  used  to  such  an  ex- 
tent as  to  mask  the  natural  flavors  of  foods,  and  to  con- 
ceal poor  cooking  and  preparation  or  poor  quality.  For 
the  microscopic  study  of  spices  the  student  is  referred  to 
Winton,  "  Microscopy  of  Vegetable  Foods,"  and  Leach, 
"  Food  Inspection  and  Analysis." 

205.  Pepper.  — Black  and  white  pepper  are  the  fruit 
of  the  pepper  plant  (Piper  nignim\  a  climbing  perennial 
shrub  which  grows  in  the  East  and  West  Indies,  the 
greatest  production  being  in  Sumatra.  For  the  black 
pepper,  the  berry  is  picked  before  thoroughly  ripe  ;  for 
the  white  pepper,  it  is  allowed  to  mature.  White  pepper 
has  the  black  pericarp  or  hull  removed.  Pepper  owes 
its  properties  to  an  alkaloid,  piperine,  and  to  a  volatile 
oil.  In  the  black  pepper  berries  there  is  present  ash  to 
the  extent  of  about  4.5  per  cent,  it  ought  not  to  be 
above  6.5  per  cent;  ether  extract,  including  piperine  and 
resin,  not  less  than  6.5  per  cent;  crude  fiber  not  more 
than  16  per  cent ;  also  some  starch  and  nitrogenous 
material.  The  white  pepper  contains  less  ash  and  cel- 
lulose than  the  black  pepper.  Ground  pepper  is  fre- 
quently grossly  adulterated  ;  common  adulterants  being  : 
cracker  crumbs,  roasted  nut  shells  and  fruit  stones, 


VINEGAR,    SPICES,    AND    CONDIMENTS  199 

charcoal,  corn  meal,  pepper  hulls,  mustard  hulls,  and 
buckwheat  middlings.  The  pepper  berries  wrinkle  in 
drying,  and  this  makes  it  difficult  to  remove  the  sand 
which  may  have  adhered  to  them.  An  excessive  amount 
of  sand  in  the  ash  should  be  classed  as  adulteration. 
Adulterants  in  pepper  are  detected  mainly  by  the  use 
of  the  microscope.  The  United  States  standard  for  pep- 
per is:  not  more  than  7  per  cent  total  ash,  15  per  cent 
fiber,  and  not  less  than  25  percent  starch  and  6  per  cent 
non-volatile  ether  extract.71 

206.  Cayenne.  —  Cayenne  or  red  pepper  is  the  fruit 
pod  of    a  plant,  capsicum^   of  which  there  are  several 
varieties,  —  the  small-fruited  kind,  used  to  make  cayenne 
or  red  pepper;  and  the  tabasco  sort,  forming  the  basis  of 
tabasco  sauce.       It  is  grown  mainly  in  the  tropics,  and 
was    used  there    as   a  condiment    before  the   landing 
of    Columbus,    who  took    specimens  back    to  Europe. 
Cayenne  pepper  contains  25  per  cent  of  oil,  about  7  per 
cent  of  ash,  and  a  liberal  amount  of  starch.     The  adul- 
terants are  usually  of  a  starchy  nature,  as  rice  or  corn 
meal,  and  the  product  is  often  colored  with  some  red 
dye. 

207.  Mustard.  —  Mustard  is  the  seed  of  the  mustard 
plant,    and  is  most  often  found   in  commerce   in   the 
ground  form.      The  black  or  brown  mustard  has  a  very 
small   seed    and  the  most   aroma.     White  mustard   is 
much  larger  and  is  frequently  used  unground.       For  the 
ground  mustard,  only  the  interior  of  the  seed  is  used,  the 


200       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

husk  being  removed  in  the  bolting.  Mustard  contains 
a  large  amount  of  oil,  part  of  which  is  usually  expressed 
before  grinding,  and  this  is  the  form  in  which  spice 
grinders  buy  it.  In  mustard  flour  there  is :  ash  from 
4  to  6  per  cent,  volatile  oil  from  0.5  to  2  per  cent,  fixed  oil 
from  15  to  25  per  cent,  crude  fiber  from  2  to  5  per  cent, 
albuminoids  from  35  to  45  per  cent,  and  a  little  starch. 
The  principal  adulterants  are  wheat,  corn,  and  rice  flour. 
When  these  are  used,  the  product  is  frequently  colored 
with  turmeric,  a  harmless  vegetable  coloring  material. 

208.  Ginger.  —  Ginger  is  the  rhizome  or  root  of  a 
reed-like  plant  (Zingiber  officinale\  native  in  tropical 
Asia,  chiefly  India.  It  is  cultivated  in  nearly  all  tropical 
countries.  When  unground  it  usually  occurs  in  two 
forms :  dried  with  the  epidermis,  or  with  the  epidermis 
removed,  when  it  is  called  scraped  ginger.  Very  fre- 
quently a  coating  of  chalk  is  given,  as  a  protection 
against  the  drug  store  beetle.  Jamaica  ginger  is  the 
best  and  most  expensive.  Cochin,  scraped,  African,  and 
Calcutta  ginger  range  in  price  in  the  order  given.  Gin- 
ger contains  from  3.6  to  7.5  per  cent  of  ash,  from  1.5  to 
3  per  cent  of  volatile  oil,  and  from  3  to  5.5  per  cent  of 
fixed  oil.  There  is  a  large  amount  of  starch.  The  chief 
adulterants  are  rice,  wheat,  and  potato  starch,  mustard 
hulls,  exhausted  ginger  from  ginger-ale  and  extract 
factories,  sawdust  and  ground  peanutshells,  and  tur- 
meric is  frequently  used  for  coloring  the  product.  The 
United  States  standard  for  ginger  is  not  more  than  42 


VINEGAR,    SPICES,    AND    CONDIMENTS  2OI 

per  cent  starch,  8  per  cent  fiber,  and  6  per  cent  total 
ash.71 

209.  Cinnamon   and   Cassia.  —  The  bark   of   several 
species   of   plants   growing   in   tropical    countries   fur- 
nishes   these   spices.     True    cinnamon   is  a   native   of 
Ceylon,  while  the  cassias  are  from  Bengal  and  China. 
In  this  country  there  is  more  cassia  used  than  cinna- 
mon —  cinnamon  being   rarely   found    except   in    drug 
stores.     Cassia   bark  is  much   thicker   than    cinnamon 
bark.     The  ground  spice  contains  about  1.5    per  cent 
volatile   oil   and   the   same  amount  of  fixed  oil,  4  per 
cent  of  ash,  and  some   fiber,  nitrogenous    matter,  and 
starch.       Cereals,    cedar     sawdust,    ground    nutshells, 
oil  meal,  and  cracker  crumbs  are  the  chief  adulterants. 

210.  Cloves.  —  Cloves   are   the    flower    buds    of    an 
evergreen   tree   that  grows  in  the  tropics.     These  are 
picked  by  hand    and    dried  in  the  sun.     In  the  order 
of   value,    Penang,   Sumatra,    Amboyna,  and   Zanzibar 
furnish    the    chief    varieties.      Cloves     rarely    contain 
more   than  8  per  cent   ash,  or  less   than   10  per   cent 
volatile  oil  and  4  per  cent  fixed  oil,  and  1 6  to  20  per 
cent  of  tannin-yielding  bodies.     No    starch  is  present. 
The    chief    adulterants     of    ground    cloves    are   spent 
cloves,  allspice,  and   ground    nutshells.      Clove    stems 
are   also    sometimes   used   and   may  be  detected  by  a 
microscopical    examination,    since    they   contain   many 
thick-walled  cells  and  much  fibrous  tissue. 


202        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

211.  Allspice.  —  Allspice,  or  pimento,  is  the  fruit  of 
an    evergreen   tree    common   in    the    West   Indies.     It 
is    a   small,  dry,  globular   berry,  two-celled,    each    cell 
having  a  single  seed.     Allspice  contains  about  2.5  per 
cent  volatile  oil,  4  per  cent  fixed  oil,  and  4.5  per  cent 
ash.     Because   of   its    cheapness,    it   is   not    generally 
adulterated,  cereal   starches   being   the   most   common 
adulterants. 

212.  Nutmeg.  —  Nutmeg   is   the    interior    kernel    of 
the    fruit  of  a  tree  growing  in  the  East  Indies.     The 
fruit    resembles   a   small    pear.     A    fleshy    mantle    of 
crimson    color,    which    is    mace,   envelopes    the    seed. 
Nutmeg  contains  about  2.2  per  cent  ash,  2.5  to  5  per 
cent   volatile   oil,    and   25    to    35    per    cent    fixed    oil. 
Mace   has   practically   the  same   composition.     Exten- 
sive   adulteration    is    seldom     practiced.      The    white 
coating  on  the  surface  of  the  nutmeg  is  lime,  used  to 
prevent  sprouting  of  the  germ. 


CHAPTER   XIV 


TEA,  COFFEE,  CHOCOLATE,  AND  COCOA 

213.  Tea  is  the  prepared  leaf  of  an  evergreen  shrub 
or  small  tree  cultivated  chiefly  in  China  and  Japan. 
There  are  two  varieties  of  plants. 
The  Assamese,  which  requires 
a  very  moist,  hot  climate,  yields 
in  India  and  Ceylon  about  400 
pounds  per  acre,  and  may  pro- 
duce as  high  as  1000  pounds. 
From  this  plant  a  number  of 
flushes  or  pickings  are  secured 
in  a  year.  The  Chinese  plant 
grows  in  cooler  climates  and  has 
a  smaller,  tougher,  and  darker 
leaf,  which  is  more  delicate  than 
that  of  the  Assamese  and  is 
usually  made  into  green  tea. 
The  Chinese  tea  plant  yields 
only  four  or  five  flushes  a  year. 
About  40  per  cent  of  the  tea 
used  in  this  country  comes  from 
Japan  and  50  per  cent  from  China.  The  tea  industry 
of  India  and  Ceylon  has  developed  rapidly  in  late  years, 
and  is  now  second  only  to  that  of  China.  Tea  has  been 
raised  upon  a  small  scale  in  the  United  States.  The 
quality  or  grade  of  the  tea  depends  upon  the  leaves 
us^ed  and  the  method  of  curing. 

203 


FIG.  53.  — TEA  LEAF. 
(After  WINTON.) 


204       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 


214.  Composition  of  Tea.  —  Black  and  green  teas 
are  produced  from  the  same  species  of  plant,  but  owe 
their  difference  in  color  as  well  as  flavor  and  odor  to 
methods  of  preparation.  The  same  plant  may  yield 
several  grades  of  both  green  and  black  tea.  To  pro- 
duce black  tea,  the  leaves  are  bruised  to  liberate  the 
juices,  allowed  to  ferment  a  short  time,  which  develops 
the  color,  and  then  dried.73  For  green  tea  the  fresh 
leaves  are  roasted  or  steamed,  then  rolled  and  dried 
as  quickly  as  possible  to  prevent  fermentation.  The 
smaller  leaves  and  the  first  picking  produce  the  finest 
quality  of  tea.  The  characteristic  flavor  and  odor  of 
tea  are  imparted  by  a  volatile  oil,  although  the  odor  is 
sometimes  altered  by  the  tea  being  brought  in  contact 
with  orange  flowers,  jessamine,  or  the  fragrant  olive. 
There  are  also  present  in  tea  an  alkaloid,  theine,  which 
gives  the  peculiar  physiological  properties,  and  tannin, 
upon  which  depends  largely  the  strength  of  the  tea 
infusion.  The  composition  of  tea  is  as  follows  : 


ORIGINAL 
TEA 

GREEN  TEA 

BLACK  TEA 

Tannin,  per  cent    

12.  QI 

IO.64. 

4.8q 

Theine,  per  cent    ..... 

3.3O 

3.  2O 

<4>.uy 
•2.  ?o 

Ash,  per  cent    

4..Q7 

A.Q2 

4.Q7 

Fiber,  per  cent  

IO.4.4. 

10.06 

IO.O7 

Protein,  per  cent  (all  insoluble) 

37-33 

3743 

38.90 

It   will  be  noticed  that  green  tea  contains  twice  as 
much   tannin   as    black   tea ;    during  the   fermentation 


TEA,    COFFEE,    CHOCOLATE,    AND    COCOA  205 

which  the  black  tea  undergoes,  some  of  the  tannin  is 
decomposed.  There  is  a  large  amount  of  protein  in 
tea,  but  it  is  of  no  food  value,  because  of  its  insolu- 
bility. About  half  of  the  ash  is  soluble.  The  tannin 
is  readily  soluble,  and  for  this  reason  green  tea  es- 
pecially should  be  infused  for  a  very  short  time  and 
never  boiled.  Tannin  in  foods  in  large  amounts 
may  interfere  with  the  normal  digestion  of  the  protein 
compounds,  because  it  coagulates  the  albumin  and 
peptones  after  they  have  become  soluble,  and  thus 
makes  additional  work  for  the  digestive  organs. 

215.  Judging  Teas.  —  Teas  are  judged  according  to  : 
(i)the  tea  as  it  appears  prepared  for  market,  (2)  the 
infusion,    and   (3)   the   out-turn    after    infusion.      The 
color  should  be  uniform ;  if  a  black  tea,  it  should   be 
grayish   black,  not  a  dead  black.     The  leaves   should 
be  uniform  in  size  or  grade.      The  quality  and  grade 
are   dependent    upon    flavor,    and,   with    the    strength 
of  the  infusion,  are  determined  by  tasting.     This  work 
is  rapidly  done  by  the  trained  tea  taster.     The   out- 
turn  should  be  of  one  color;  no  bright  green  leaves 
should   be   present ;    evenness  of   make   is  judged   by 
the  out-turn.     The  flavor  of  a  tea  is  largely  a  matter 
of  personal  judgment,  but  from  a  physiological  point 
of  view  black  teas  are  given  the  preference. 

216.  Adulteration   of   Tea.  —  A    few   years   ago   tea 
was  quite  extensively  adulterated,  but  the  strict  regu- 
lation of  the  government  regarding  imported   tea  has 


206        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

greatly  lessened  adulteration.  The  most  common  form 
was  the  use  of  spent  leaves,  i.e.  leaves  which  had 
been  infused.  Leaves  of  the  willow  and  other  plants 
which  resemble  tea  were  also  used,  as  well  as  large 
quantities  of  tea  stems.  Facing  or  coloring  is  also 
an  adulteration,  since  it  is  done  to  give  poor  or 
damaged  tea  a  brighter  appearance.  "  Facing  con- 
sists in  treating  leaves  damaged  in  manufacture  or 
which  from  age  are  inferior,  with  a  mixture  contain- 
ing  Prussian  blue,  turmeric,  indigo,  or  plumbago  to 
impart  color  or  gloss,  and  with  a  fraudulent  intent. 
There  is  no  evidence  that  the  facing  agents  are 
deleterious  to  health  in  the  small  quantities  used,  but  as 
they  are- used  for  purposes  of  deception,  they  should  be 
discouraged."  73  Facing  and  the  addition  of  stems  are 
the  chief  adulterations  practiced  at  present. 

217.   Food  Value  and  Physiological  Properties  of  Tea. 

—  Tea  infusion  does  not  contain  sufficient  nutrients 
to  entitle  it  to  be  classed  as  a  food.  It  is  with  some 
persons  a  stimulant.  The  caffein  or  theine  in  tea  is 
an  alkaloid  that  has  characteristic  physiological  proper- 
ties. In  doses  of  from  three  to  five  grains,  accord- 
ing to  the  United  States  Dispensatory,  "  it  produces 
peculiar  wakefulness."  Larger  doses  produce  intense 
physical  restlessness,  mental  anxiety,  and  obstinate 
sleeplessness.  "  It  has  no  effect  upon  the  motor 
nerves,  but  is  believed  to  have  a  visible  effect  upon 
the  sensatory  nerves."  (United  States  Dispensatory.) 


TEA,    COFFEE,    CHOCOLATE,    AND    COCOA 


207 


Experiments  with  animals  show  that  it  causes  eleva- 
tion of  the  arterial  pressure.  It  is  used  as  a  cardiac 
stimulant.  The  quantity  of  theine  consumed  in  a  cup 
of  tea  is  about  ^  of  a  grain,  or  ^  of  a  medicinal  dose. 


*  * 


3. 


FIG.  54.  — COFFEE  BERRIES. 
i,  Mocha;  2,  Java;  3,  Rio. 

218.  Composition  of  Coffee. — The  coffee  tree  is  an 
evergreen  cultivated  in  the  tropics.  It  grows  to  a  height 
of  30  feet,  but  when  cultivated  is  kept  pruned  to  from 
6  to  10  feet.  The  fruit,  which  resembles  a  small  cherry, 
with  two  seeds  or  coffee  grains  embedded  in  the  pulp, 
is  dried  and  the  seeds  removed,  cleaned,  and  graded. 
Coffee  has  an  entirely  different  composition  from  tea ; 


208      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


it  is  characterized  by  a  high  per  cent  of  fat  and  soluble 
carbohydrates,  and  also  contains  an  essential  oil  and 
caffein,  an  alkaloid  identical  with  theine.  Tannic  acid, 
not  as  free  acid,  is  combined  with  caffein  as  a  tannate. 


RAW  COFFEE 

ROASTED  COFFEE 

Water     

Per  Cent 
11.2^ 

Per  Cent 
I  .  I  c 

Ash    

•3.Q2 

4  7S 

Fat     
Sugar,  etc  
Protein  

12.27 

0.66 

12.  07 

14.48 
•       8.55 

n  08 

Caffein    

1.  21 

I   ">A. 

The  high  per  cent  of  sugar  and  other  soluble  carbohy- 
drates in  roasted  coffee  is  caused  by  the  action  of  heat 
upon  the  non-nitrogenous  compounds.  Coffee  cannot 
be  considered  a  food,  because  only  a  comparatively  small 
amount  of  the  nutrients  are  soluble  and  available.  It  is 
a  mildly  stimulating  beverage.  With  some  individuals 
it  appears  to  promote  the  digestive  process,  while  with 
others  its  effect  is  not  beneficial.  Coffee  is  more  exten- 
sively used  in  this  country  than  tea,  and  is  subject  to 
greater  adulteration.  It  is  adulterated  by  facing  and 
glazing;  i.e.  coloring  the  berries  to  resemble  different 
grades  and  coating  them  with  caramel  and  dextrine. 
Spent  coffee  grains  and  coffee  that  has  been  extracted 
without  grinding  are  also  used  as  adulterants.  Imitation 
berries  made  of  rye,  corn,  or  wheat  paste,  molded, 
colored  with  caramel,  and  baked  have  been  found  mixed 


TEA,    COFFEE,    CHOCOLATE,    AND    COCOA  2OQ 

with  genuine  coffee  berries.  Roasted  cereals  and  chic- 
ory are  used  extensively  to  adulterate  ground  coffee. 
Chicory  is  prepared  from  the  root  of  the  chicory  plant, 
which  belongs  to  the  same  family  as  the  dandelion.  It 
is  claimed  by  some  that  a  small  amount  of  chicory  im- 
proves the  flavor  of  coffee.  However,  when  chicory  is 
added  to  coffee,  it  should  be  so  stated  on  the  label  and 
the  amount  used  given.  The  dextrine  and  sugar  used 
in  glazing  are  browned  or  caramelized  during  roasting 
and  impart  a  darker  color  to  the  infusion,  making  it  ap- 
pear better  than  it  really  is.  The  glazing  also  makes 
the  coffee  retain  moisture  which  would  otherwise  be 
driven  off  during  roasting.  Coffee  contains  such  a  large 
per  cent  of  oil  that  the  berries  generally  float  when  thrown 
on  water,  while  the  imitation  berries  sink.  Chicory  also 
sinks  rapidly  and  colors  the  water  brown,  while  the  cof- 
fee remains  floating  for  some  time. 

There  are  three  kinds  of  coffee  in  general  use :  Java, 
Mocha,  and  Rio  or  Brazil.  The  Brazil  coffee  has 
the  largest  berry  and  is  usually  styled  by  dealers  as 
"low"  or  "low  middlings."  The  Java  coffee  berries  are 
smaller  and  paler  in  color,  the  better  grades  being 
brown.  Mocha  usually  commands  the  highest  price  in 
commerce.  The  seeds  are  small  and  dark  yellow 
before  roasting. 

219.   Cereal  Coffee  Substitutes. 

"  A  few  of  these  preparations  contain  a  little  true  coffee,  but  for 
the  most  part  they  appear  to  be  made  of  parched  grains  of  barley, 
wheat,  etc.,  or  of  grain  mixed  with  pea  hulls,  ground  corncobs,  or 
p 


210      HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

wheat  middlings.  It  is  said  that  barley  or  wheat  parched,  with  a 
little  molasses,  in  an  ordinary  oven,  makes  something  indistinguish- 
able in  flavor  from  some  of  the  cereal  coffees  on  the  market.  If  no 
coffee  is  used  in  the  cereal  preparations,  the  claim  that  they  are  not 
stimulating  is  probably  true.  As  for  the  nutritive  value,  parching 
the  cereals  undoubtedly  renders  some  of  the  carbohydrates  soluble, 
and  a  part  of  this  soluble  matter  passes  into  the  decoction,  but  the 
nutritive  value  of  the  infusion  is  hardly  worth  considering  in  the 
.dietary."56 

220.  Cocoa  and  Chocolate  Preparations.  —  Cocoa  and 
chocolate  are  manufactured  from  the  "cocoa  bean," 
the  seed  of  a  tree  native  to  tropical  America.  The 
beans  are  inclosed  in  a  lemon-yellow,  fleshy  pod.  They 
are  removed  from  the  pulp,  allowed  to  undergo  fermen- 
tation, and  dried  by  exposure  to  the  air  and  light,  which 
hardens  them  and  gives  them  a  red  color.  This  method 
produces  what  is  known  as  the  "fermented  cocoa." 
For  the  "  unfermented  cocoa,"  the  beans  are  dried  with- 
out undergoing  fermentation.  Fermentation  removes 
much  of  the  acidity  and  bitterness  characteristic  to  the 
unfermented  bean,  and  when  properly  regulated  develops 
flavor.  The  original  bean  contains  about  50  per  cent 
fat,  part  of  which  is  removed  in  preparing  the  cocoa. 
This  fat  is  sold  as  cocoa  butter.  In  the  preparation  of 
some  brands  of  cocoa,  alkalies,  such  as  soda  and  potash, 
are  used  to  form  a  combination  with  the  fat  to  prevent 
its  separating  in  oily  globules.  This  treatment  improves 
the  appearance  of  the  cocoa,  but  experiments  show  the 
albumin  to  be  somewhat  less  digestible  and  the  soap- 
like  product  resulting  not  as  a  valuable  food  as  the 


TEA,    COFFEE,    CHOCOLATE,    AND    COCOA  211 

fat.  Such  preparations  have  a  high  per  cent  of  ash. 
There  is  no  objection  from  a  nutritive  point  of  view 
to  a  cocoa  in  which  the  fat  separates  in  oily  globules. 

221.  Composition  of  Cocoa. — The  cocoa  bean,  when 
dried  or  roasted  and  freed  from  its  husk  and  ground,  is 
sold  as  cracked  cocoa,  or  cocoa  nibs.  From  cocoa  nibs 
the  various  cocoa  and  chocolate  preparations  are  made. 
Cocoas  vary  in  composition  according  to  the  extent  to 
which  the  fat  is  removed  during  the  process  of  manu- 
facture and  the  nature  and  extent  to  which  other  ingre- 
dients are  added.  An  average  cocoa  contains  about  20 
per  cent  of  proteids,  and  30  per  cent  fat,  also  starch, 
sugar,  gums,  fiber,  and  ash,  as  well  as  theobromine,  a 
material  very  similar  to  theine  and  caffein  in  tea  and 
coffee,  but  not  such  an  active  stimulant.  Cocoa  is  not 
easily  soluble,  but  it  may  be  ground  so  fine  that  a  long 
time  is  required  for  its  sedimentation;  or  sugar  or  other 
soluble  material  may  be  added  during  the  process  of 
manufacture  to  increase  the  specific  gravity  of  the  liq- 
uid to  such  an  extent  that  the  same  object  is  attained 
without  such  fine  grinding.  The  first  method  is  to  be 
preferred.  Cocoa  and  its  preparations  are  richer  in 
nutritive  substances  than  tea  and  coffee  and  have  this 
added  advantage  that  both  the  soluble  and  insoluble 
portions  become  a  part  of  the  beverage.  Owing  to  the 
small  amount  used  for  a  cup  of  cocoa,  independent  of 
the  milk  it  does  not  add  much  in  the  way  of  nutrients 
to  the  ration. 


212       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


222.  Chocolate.  —  Plain  chocolate  is  prepared  from 
cocoa  nibs  without  "  removal  of  the  fat  or  other  constit- 
uents except  the  germ."  It  differs  in  chemical  com- 
position from  cocoa  by  containing  more  fat  and  less 
protein ;  it  has  nearly  the  same  chemical  composition  as 
the  cocoa  nibs.  It  is  officially  denned  as  containing 
"  not  more  than  3  per  cent  of  ash  insoluble  in  water, 
3|-  per  cent  of  crude  fiber  and  9  per  cent  of  starch,  and 
less  than  45  per  cent  cocoa  fat."  71 

By  the  addition  of  sugar,  sweet  chocolates  are  made. 
They  vary  widely  in  composition  according  to  the  fla- 
vors and  amounts  of  sugar  added  during  their  prepara- 
tion. The  average  composition  of  cocoa  nibs,  standard 
cocoa,  and  plain  chocolate  is  as  follows: 


COCOA 
NIBS 

COMPOSITION  OF 
STANDARD  COCOA 

COMPOSITION  OF 
PLAIN  CHOCOLATE 

Water      

Per  Cent 
T..OO 

Per  Cent 

Per  Cent 
T..OQ 

Ash     

^.SO 

4-2O 

3.08 

Theobromine    .     .     . 
Caffein     

I.OO 
O.  CO 

Crude  Protein  .     .     . 
Crude  fiber  .... 
Fat      . 

12.00 
2.50 
cn.OO 

5.02 
72.  C2 

2.63 

4Q.8l 

Starch  and  other  non- 
nitrogenous  matter  . 

$v.w 
27.50 

223.  Adulteration  of  Chocolate  and  Cocoa.  —  The  vari- 
ous chocolate  and  cocoa  preparations  offer  an  enticing 
field  for  sophistication;  they  are  not,  however,  so  exten- 


TEA,    COFFEE,    CHOCOLATE   AND    COCOA 


213 


sively  adulterated  as  before  the  enforcement  of  national 
and  state  pure  food  laws.  The  most  common  adulter- 
ants are  starch,  cocoa  shells,  and  occasionally  iron  dioxid 
and  other  pigments  to  give  color,  also  foreign  fats 
to  replace  the  fat  removed  and  to  give  the  required 
plasticity  for  molding. 

224.    Comparative   Composition   of    Beverages.  —  Tea 

and  coffee  as  beverages  contain  but  little  in  the  way  of 
nutrients  other  than  the  cream  and  sugar  used  in  them. 
The  solid  matter  in  tea  and  coffee  infusions  amounts  to 
less  than  1.2  per  cent.  When  cocoa  is  made  with  milk, 
it  is  a  beverage  of  high  nutritive  value  due  mainly  to 

the  milk. 

COMPOSITION  OF  BEVERAGES  56 


KIND  OF  BEVERAGE 

WATER 

PROTEIN 

FAT 

CARBO- 
HYDRATES 

FUEL 
VALUE 
PER  LB. 

Commercial  cereal  coffee  (0.5 
ounce  to  I  pint  water)  .     . 
Parched    corn    coffee      (1.6 
ounces  to  I  pint  water) 
Oatmeal  water  (i  ounce  to  I 
pint  water)     .... 

Per  Cent 
98.2 

99-5 

QQ.7 

Per  Cent 
0.2 
0.2 
O  3 

Per  Cent 

Per  Cent 
14 
0.5 
O  1 

Calories 
30 

!3 

1  1 

Coffee    (i    ounce   to    i    pint 
water)  

W*/ 
Q8  Q 

^•J 

O  2 

U'J 

O  7 

16 

Tea   (0.5    ounce    to    i    pint 
water)  

yo.y 
QQ.  £ 

O.2 

06 

1C 

Cocoa  (0.5  ounce  to   i  pint 
milk)    

84.  C 

1.8 

A  .7 

6.0 

l6c 

Cocoa  (0.5  ounce  to  i   pint 
water)  

Q7.  1 

o  6 

O  Q 

I.I 

6c 

Skimmed  milk   

y/  •  L 

QO.C 

3.4 

O.I 

5.1 

1  70 

CHAPTER   XV 
THE  DIGESTIBILITY  OF  FOODS 

225.  Digestibility,  How  Determined.  —  The  term 
"  digestibility,"  as  applied  to  foods,  is  used  in  two 
ways:  (i)  meaning  the  thoroughness  of  the  process, 
or  the  completeness  with  which  the  nutrients  of  the 
food  are  absorbed  and  used  by  the  body,  and  (2)  mean- 
ing the  ease  or  comfort  with  which  digestion  is  accom- 
plished. Cheese  is  popularly  termed  indigestible,  and 
rice  digestible,  when  in  reality  the  nutrients  of  cheese 
are  more  completely  although  more  slowly  digested 
than  those  of  rice.  In  this  work,  unless  otherwise 
stated,  digestibility  is  applied  to  the  completeness  of 
the  digestion  process. 

The  digestibility  of  a  food  is  ascertained  by  means  of 
digestion  experiments,  in  which  all  of  the  food  consumed 
for  a  certain  period,  usually  two  to  four  days,  is  weighed 
and  analyzed,  and  from  the  weight  and  composition  is 
determined  the  amount,  in  pounds  or  grams,  of  each  nu- 
trient consumed.72  In  like  manner  the  nutrients  in  the 
indigestible  portion,  or  feces,  are  determined  from  the 
weight  and  composition  of  the  feces.  The  indigestible 

214 


THE    DIGESTIBILITY    OF    FOODS 


2I5 


nutrients  in  the  feces  are  deducted  from  the  total  nu- 
trients of  the  food,  the  difference  being  the  amount 
digested,  or  oxidized  in  the  body.  When  the  food  is  di- 
gested, the  various  nutrients  undergo  complete  or  partial 
oxidation,  with  the  formation  of  carbon  dioxid  gas,  water, 
ure'a  (CH4N2O),  and  other  compounds.  The  feces  con- 
sist mainly  of  the  compounds  which  have  escaped  diges- 
tion. The  various  groups  of  compounds  of  foods  do  not 
all  have  the  same  digestibility  ;  for  example,  the  starch 
of  potatoes  is  92  per  cent  digestible,  while  the  protein 
is  only  72  per  cent.  The  percentage  amount  of  a 
nutrient  that  is  digested  is  called  the  digestion  coeffi- 
cient. 

In  the  following  way  the  digestibility  of  a  two-days 
ration  of  bread  and  milk  was  determined  :  7/3.5  grams 
of  bread  and  2000  grams  of  milk  were  consumed  by  the 
subject.  The  dried  feces  weighed  38.2  grams.  The  foods 
and  feces  when  analyzed  were  found  to  have  the  follow- 
ing composition  : 62 


COMPOSITION 

BREAD 

MILK 

FECES* 

Water  

A  A    I  7 

86  52 

Crude  protein     

^M--1  J 

7  7C 

».YC 

25  88 

Ether  extract      

/  */  j 
O.QO 

j'  LJ 

A    6"* 

18  23 

Ash      .     .     . 

^•y^ 
O   12 

tt'VJ 

o  70 

26  ic. 

Carbohydrates    

V'3<6 
4.6.  QO 

c.OO 

^U.Ji) 

2Q.  C  A 

Calories  per  gram    

2.  4.  SO 

O.7Q 

r  08^ 

*  Results  on  dry- matter  basis. 


2l6       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


STATEMENT  OF  RESULTS  OF  A  DIGESTION  EXPERIMENT 


FOOD  CONSUMED 

WEIGHT  OF 
MATERIAL 

PROTEIN 

N  x  6.25 

ETHER 
EXTRACT 

CARBOHY- 
DRATES 

s 

(/} 

«< 

HEAT  OF 

COMBUS- 
TION 

Bread    

Grams 
777.  C 

Grams 
6o.O 

Grams 

6.0 

Grams 
^62.8 

Grams 
2.C 

Calories 
180: 

Milk      

2OOO.O 

6^.O 

Q2.6 

IOO.O 

IJ.  O 

ic8c 

Total    .... 
Feces    

38.2 

123.0 
Q.Q 

99-5 

7.O 

462.8 

II.  ^ 

16.5 

I  O.I 

3480 
IQ4. 

Total  amount  digested 

II3-I 

92.5 

45J-5 

6.4 

3286 

Per    cent    digested    or 

coefficients  of  diges- 
tibility     

Q2.O 

Q7.O 

Q7.C 

•?8.8 

QA.A 

Available  energy      .     . 

QO.O 

In  this  experiment  92  per  cent  of  the  crude  protein, 
93  per  cent  of  the  ether  extract,  and  97.5  per  cent  of 
the  carbohydrates  of  the  bread  and  milk  ration  were 
digested  and  absorbed  by  the  body.  In  calculating  the 
available  energy,  correction  is  made  for  the  unoxidized 
residue,  as  urea  and  allied  forms.  It  is  estimated  that 
for  each  gram  of  protein  in  the  ration  there  was  an  in- 
digestible residue  yielding  1.25  calories. 

226.  Available  Nutrients.  —  A  food  may  contain  a 
comparatively  large  amount  of  a  compound,  and  yet, 
on  account  of  its  low  digestibility,  fail  to  supply  much 
of  it  to  the  body  in  an  available  form.  Hence  it  is 


THE    DIGESTIBILITY   OF    FOODS  217 

that  the  value  of  a  food  is  dependent  not  alone  on  its 
composition,  but  also  on  its  digestibility.  The  digestible 
or  available  nutrients  of  a  food  are  determined  by  mul- 
tiplying the  per  cent  of  each  nutrient  which  the  food 
contains  by  its  digestion  coefficient.  For  example,  a 
sample  of  wheat  flour  contains  12  per  cent  protein, 
88  per  cent  of  which  is  digestible,  making  10.56  per 
cent  of  available  or  digestible  protein  (12  x  0.88  —  10.56). 
Graham  flour  made  from  similar  wheat  contains  13  per 
cent  total  protein,  and  only  75  per  cent  of  the  protein  is 
digestible,  making  9.75  per  cent  available  (13  x  0.75  = 
9.75).  Thus  one  food  may  contain  a  larger  total  but  a 
smaller  available  amount  of  a  nutrient  than  another. 

227.  Available  Energy.  —  The  available  energy  of  a 
food  or  a  ration  is  expressed  in  calories.  A  ration  for  a 
laborer  at  active  out-of-door  work  should  yield  about  3200 
calories.  The  calory  is  the  unit  of  heat,  and  represents 
the  heat  required  to  raise  the  temperature  of  a  kilo- 
gram of  water  i°  C.,  or  four  pounds  of  water  i°  F.  The 
caloric  value  of  foods  is  determined  by  the  calorimeter, 
an  apparatus  which  measures  heat  with  great  accuracy. 
A  pound  of  starch,  or  allied  carbohydrates,  yields  1860 
calories,  and  a  pound  of  fat  4225  (see  Section  13).  While 
a  gram  of  protein  completely  burned  produces  7.8 
calories,  digested  it  yields  only  about  4.2  calories,  be- 
cause, as  explained  in  the  preceding  section,  not  all  of 
the  carbon  and  oxygen  are  oxidized.59  The  caloric 
value  or  available  energy  of  a  ration  can  be  calculated 


FIG.  55.— CALORIMETER. 
218 


THE    DIGESTIBILITY    OF    FOODS  219 

from  the  digestible  nutrients  by  multiplying  the  pounds 
of  digestible  protein  and  carbohydrates  by  1860,  the 
digestible  fat  by  4225,  and  adding  the  results.  For 
determination  of  the  available  energy  of  foods  under 
different  experimental  conditions,  and  where  great  ac- 
curacy is  desired,  a  specially  constructed  respiration 
calorimeter  has  been  devised,  which  is  built  upon  the 
same  principle  as  an  ordinary  calorimeter,  except  it  is 
large  enough  to  admit  a  person,  and  is  provided  with 
appliances  for  measuring  and  analyzing  the  intake  and 
outlet  of  air.74  The  heat  produced  by  the  combustion 
of  the  food  in  the  body  warms  the  water  surrounding 
the  calorimeter  chamber,  and  this  increase  in  tempera- 
ture is  determined  by  thermometers  reading  to  0.005  of 
a  degree  or  less. 

228.  Normal  Digestion  and  Health.  —  While  the  pro- 
cess of  digestion  has  been  extensively  studied,  it  is  not 
perfectly  understood.  Between  the  initial  compounds 
of  foods  and  their  final  oxidation  products  a  large  num- 
ber of  intermediate  substances  are  formed,  and  when 
digestion  fails  to  take  place  in  a  normal  way,  toxic  or 
poisonous  compounds  are  produced  and  various  diseases 
result.  It  is  probable  that  more  diseases  are  due  to 
imperfect  or  malnutrition  than  to  any  other  cause. 
There  is  a  very  close  relationship  between  health  and 
normal  digestion  of  the  food. 

The  cells  in  the  different  parts  of  the  digestive 
tract  secrete  fluids  containing  substances  known  as 


220       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

soluble  ferments,  or  enzymes,  which  act  upon  the  vari- 
ous compounds  of  foods,  changing  them  chemically  and 
physically  so  that  they  can  be  absorbed  and  utilized  by 
the  body.  (See  Section  31.)  Some  of  the  more  impor- 
tant ferments  are:  ptyolin  of  the  saliva,  pepsin  of  the 
stomach,  and  pancreatin  and  diastase  of  the  intestines. 
In  order  that  these  ferments  may  carry  on  their  work  in 
a  normal  way,  the  acidity  and  alkalinity  of  the  diffe rent- 
parts  of  the  digestive  tract  must  be  maintained.  The 
gastric  juice  contains  from  o.i  to  0.25  per  cent  of  hydro- 
chloric acid,  imparting  mildly  antiseptic  properties  ;  and 
while  the  peptic  ferment  works  in  a  slightly  acid  solu- 
tion, the  tryptic  ferment  requires  an  alkaline  solution. 
To  secrete  the  necessary  amount  and  quality  of  diges- 
tive fluids,  the  organs  must  be  in  a  healthy  condition. 
Many  erroneous  ideas  regarding  the  digestion  of  foods 
are  based  upon  misinterpretation  of  facts  by  persons 
suffering  from  impaired  digestion,  and  attempts  are  fre- 
quently made  to  apply  to  normal  digestion  generaliza- 
tions applicable  only  to  diseased  conditions. 

229.  Digestibility  of  Animal  Foods.  — The  proteids 
and  fats  in  animal  foods,  as  meats,  are  more  completely 
digested  than  the  same  class  of  nutrients  in  vegetables. 
In  general,  about  95  per  cent  of  the  proteids  of  meats 
is  digestible,  while  those  in  vegetables  are  often  less 
than  85  percent  digestible.  The  amount  of  indigestible 
residue  from  animal  foods  is  small;  while  from  vege- 
tables it  is  large,  for  the  cellulose  prevents  complete 


THE    DIGESTIBILITY   OF    FOODS  221 

absorption  of  the  nutrients  and,  as  a  result,  there  is 
much  indigestible  residue.  Animal  foods  are  concen- 
trated,-in  that  they  furnish  large  amounts  of  nutrients 
in  digestible  forms.  There  is  less  difference  in  the 
completeness  with  which  various  meats  are  digested 
than  in  their  ease  of  digestion;  the  proteins  all  have 
about  the  same  digestion  coefficients,  but  vary  with 
individuals  as  to  ease  of  digestion  and  time  required. 
It  is  generally  considered  that  the  digestible  proteins, 
whether  of  animal  or  vegetable  origin,  are  equally  valu- 
able for  food  purposes.  This  is  an  assumption,  how- 
ever, that  has  not  been  well  established  by  experimental 
evidence.  In  a  mixed  ration,  the  proteins  from  different 
sources  appear  to  have  the  same  nutritive  value,  but  as 
each  is  composed  of  different  radicals  and  separated 
into  dissimilar  elementary  compounds  during  the  pro- 
cess of  digestion,  they  would  not  necessarily  all  have 
the  same  food  value. 

There  is  but  little  difference  between  the  fats  and 
proteins  of  meats  as  to  completeness  of  digestion,  —  the 
slight  difference  being  in  favor  of  the  proteins.  Some 
physiologists  claim  that  the  fat,  which  in  some  meats 
surrounds  the  bundles  of  fiber  (protein),  forming  a 
protecting  coat,  prevents  the  complete  solvent  action 
of  the  digestive  fluid.  Very  fat  meats  are  not  as 
completely  digested  as  those  moderately  fat.  It  is 
also  claimed  that  the  digestibility  of  the  meat  is  influ- 
enced by  the  mechanical  character,  as  toughness  of  the 
fiber. 


, 


222        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

230.  Digestibility  of  Vegetable  Foods.  —  Vegetable 
foods  vary  in  digestibility  with  their  mechanical  con- 
dition and  the  amount  of  cellulose  or  fiber.  In  some 
the  nutrients  are  so  embedded  in  cellular  tissue  as  to  be 
protected  from  the  solvent  action  of  the  digestive  fluids, 
and  in  such  cases  the  digestibility  and  availability  are 
low.  The  starches  and  sugars  are  more  completely 
digested  than  any  other  of  the  nutrients  of  .vegetables ; 
in  some  instances  they  are  from  95  to  98  per  cent  di- 
gestible. Some  cellular  tissue,  but  not  an  excess,  is 
desirable  in  a  ration,  as  it  exerts  a  favorable  mechanical 
action  upon  the  organs  of  digestion,  encourages  peri- 
stalsis, and  is  an  absorbent  and  dilutant  of  the  waste 
products  formed  during  digestion.  For  example,  in  the 
feeding  of  swine,  it  has  been  found  that  corn  and  cob 
meal  often  gives  better  results  than  corn  fed  alone. 
The  cob  contains  but  little  in  the  way  of  nutrients,  but 
it  exerts  a  favorable  mechanical  action  upon  digestion. 
Occasionally  too  many  bulky  foods  are  combined,  con- 
taining scant  amounts  of  nutrients,  so  that  the  body 
receives  insufficient  protein.  This  is  liable  to  be  the 
case  in  the  dietary  of  the  strict  vegetarian.  Many  of 
the  vegetables  possess  special  dietetic  value,  due  to  the 
organic  acids  and  essential  oils,  as  cited  in  the  chapter 
on  fruits  and  vegetables.  The  value  of  such  foods  can- 
not always  be  determined  from  their  content  of  digest- 
ible protein,  fat,  and  carbohydrates.  This  is  particularly 
evident  when  they  are  omitted  from  the  ration,  as  in 
the  case  of  a  restricted  diet  consisting  mainly  of  animal 


THE    DIGESTIBILITY    OF    FOODS  223 

foods.  Many  vegetables  have  low  nutritive  value  on 
account  of  their  bulky  nature  and  the  large  amount  of 
water  and  cellulose  which  they  contain,  which  tends  to 
decrease  digestibility  and  lower  the  amount  of  available 
nutrients.  Because  of  their  bulk  and  fermentable  na- 
ture, resulting  in  the  formation  of  gases,  a  diet  of  coarse 
vegetables  has  a  tendency  to  cause  distention  and  en- 
largement of  the  intestinal  organs.  The  carbohydrates, 
which  are  the  chief  constituents  of  vegetables,  are 
digested  mainly  in  the  intestines,  and  require  special 
mechanical  preparation  in  the  stomach,  hence  the  nutri- 
ents of  vegetables  are  not,  as  a  rule,  as  easily  digested 
as  those  of  animal  foods. 

231.  Factors    influencing    Digestion.  —  There    are    a 
number  of  factors  which  influence  completeness  as  well 
as  ease  of   digestion,    as:    (i)   combination   of   foods; 
(2)  amount  of  food;  (3)  method  of  preparation;  (4)  me- 
chanical condition  of  the  food ;  (5)palatability;  (6)  phys- 
iological properties;  (7)  individuality  of  the  consumer; 
and  (8)  psychological  influences. 

232.  Combination  of  Foods.  —  In  a  mixed  ration  the 
nutrients  are  generally  more  completely  digested  than 
when  only  one  food  is  used.      For  example,    milk  is 
practically  all  digested  when  it  forms  a  part  of  a  ration, 
and  it  also  promotes  digestibility  of  the  foods  with  which 
it  is  combined,  but  when  used  alone  it  is  less  digestible.27 
Bread   alone  and    milk   alone    are    not   as    completely 
digested  as  bread  and  milk  combined.      The  same  in  a 


224       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

general  way  has  been  observed  in  the  feeding  of  farm 
animals,  —  better  results  are  secured  from  combining 
two  or  more  foods  than  from  the  use  of  one  alone.  The 
extent  to  which  one  food  influences  the  digestibility  of 
another  has  not  been  extensively  studied. 

In  a  mixed  ration,  consisting  of  several  articles  of 
food  of  different  mechanical  structure,  the  work  of 
digestion  is  more  evenly  distributed  among  the  various 
organs.  A  food  often  requires  special  preparation  on 
the  part  of  the  stomach  before  it  can  be  digested  in  the 
intestines,  and  if  this  food  is  consumed  in  small  amounts 
and  combined  with  others  of  different  structure,  the 
work  of  gastric  digestion  is  lessened  so  that  the  foods 
are  properly  prepared  and  normal  digestion  takes  place. 
The  effect  which  one  food  exerts  upon  the  digestibility 
of  another  is  largely  mechanical. 

233.  Amount  of  Food.  —  Completeness  as  well  as 
ease  of  digestion  is  influenced  by  the  amount  of  food 
consumed.  In  general,  excessive  amounts  are  not  as 
completely  digested  as  moderate  amounts.  In  digestion 
experiments  with  oatmeal  and  milk,  it  was  found  that 
when  these  foods  were  consumed  in  large  quantities  the 
fat  and  protein  were  not  as  completely  absorbed  by  the 
body  as  when  less  was  used,  the  protein  being  7  per 
cent  and  the  fat  6  per  cent  more  digestible  in  the 
medium  ration.  Experiments  with  animals  show  that 
economical  results  are  not  secured  from  an  excess  of 
food.5  Some  individuals  consume  too  much  food,  and 


THE    DIGESTIBILITY    OF    FOODS  225 

with  them  a  restricted  diet  would  be  beneficial,  while 
others  err  in  not  consuming  enough  to  meet  the  re- 
quirements of  the  body.  Quite  frequently  it  is  those 
who  need  more  food  who  practice  dieting.  When  there 
is  trouble  with  digestion,  it  is  not  always  the  amount  or 
kind  of  food  which  is  at  fault,  but  other  habits  may 
be  such  as  to  affect  digestion.  The  active  out-of-door 
laborer  can  with  impunity  consume  more  food,  because 
there  is  greater  demand  for  nutrients,  and  the  food  is 
more  completely  oxidized  in  the  body  and  without  the 
formation  of  poisonous  waste  products.  The  amount  of 
food  consumed  should  be  sufficient  to  meet  all  the 
demands  of  the  body  and  maintain  a  normal  weight. 

234.  Method  of  Preparation  of  Food.  —  The  extent  to 
which  methods  of  cooking  and  preparation  influence 
completeness  of  digestion  has  not  been  extensively  in- 
vestigated. As  is  well  known,  they  have  great  influence 
upon  ease  and  comfort  of  digestion.  During  cooking, 
as  discussed  in  Chapter  II,  extensive  physical  and 
chemical  changes  occur,  and  these  in  turn  affect  digesti- 
bility. When  the  cooking  has  not  been  sufficient  to 
mechanically  disintegrate  vegetable  tissue,  the  digestive 
fluids  fail  to  act  favorably  upon  the  food.  Cooking  is 
also  beneficial  because  it  renders  the  food  sterile  and 
destroys  all  objectionable  microorganisms  which,  if  they 
remain  in  food,  readily  undergo  incubation  in  the  digest- 
ive tract,  interfering  with  normal  digestion.  Prolonged 
heat  causes  some  foods  to  become  less  digestible,  as  milk, 
Q 


226        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

which  digestion  experiments  show  to  be  more  completely 
digested  when  fresh  than  when  sterilized.  Pasteurized 
milk,  which  is  not  subjected  to  so  high  a  temperature  as 
sterilized  milk,  is  more  completely  digested.  See  Chap- 
ter VII  for  discussion  of  sterilizing  and  pasteurizing 
milk.38  TH8  benefits  derived  from  the  destruction  of 
the  objectionable  bacteria  in  foods  are,  however,  greater 
than  the  losses  attendant  on  lessened  digestibility  due 
to  the  action  of  heat.  The  method  of  preparation  of  a 
food  affects  its  digestibility  mainly  through  change  in 
mechanical  structure,  and  modification  of  the  forms  in 
which  the  nutrients  are  present.5 

235.  Mechanical  Condition  of  Foods.  —  The  mechanical 
condition  of  foods  as  to  density  and  structure  of  the 
particles  and  the  extent  to  which  they  are  disintegrated 
in  their  preparation  for  the  table  influences  digestibility 
to  a  great  extent.  The  mechanics  of  digestion  is  a 
subject  that  has  not  been  extensively  investigated,  and  it 
is  one  of  great  importance,  as  biological  and  chemical 
changes  cannot  take  place  if  the  food  is  not  in  proper 
mechanical  condition.  In  general,  the  finer  the  food 
particles,  the  more  completely  the  nutrients  are  acted 
upon  by  the  digestive  fluids  and  absorbed  by  the  body. 
Nevertheless,  the  diet  should  not  consist  entirely  of  finely 
granulated  foods.  Some  foods  are  valuable  mainly 
because  of  the  favorable  action  they  exert  mechanically 
upon  digestion,  rather  than  for  the  nutrients  they  con- 
tain.62 Coarsely  granulated  breakfast  foods,  whole 


THE    DIGESTIBILITY   OF    FOODS  227 

wheat  flour,  and  many  vegetables  contain  sufficient 
cellular  tissue  to  give  special  value  from  a  mechanical 
rather  than  a  chemical  point  of  view.  The  extent  to 
which  coarsely  and  finely  granulated  foods  should  enter 
into  the  ration  is  a  question  largely  for  the  individual  to 
determine.  Experiments  with  pigs  show  ^nat  if  large 
amounts  of  coarse,  granular  foods  are  consumed,  the 
tendency  is  for  the  digestive  tract  to  become  inflamed 
and  less  able  to  exercise  its  normal  functions.  Coarsely 
granulated  foods  have  a  tendency  to  pass  through  the 
digestive  tract  in  less  time  than  those  that  are  finely 
granulated,  due  largely  to  increased  peristaltic  action, 
and  the  result  is  the  food  is  not  retained  a  sufficient 
length  of  time  to  allow  normal  absorption  to  take  place. 
In  the  feeding  of  farm  animals,  it  has  been  found  that 
the  mechanical  condition  of  the  food  has  a  great  influ- 
ence upon  its  economic  use.  Rations  that  are  either 
too  bulky  or  too  concentrated  fail  to  give  the  best  results. 
In  the  human  ration,  the  mechanical  condition  of  the 
food  is  equally  as  important  as  its  chemical  composi- 
tion. 

236.  Mastication  is  an  important  part  of  digestion, 
and  when  foods  are  not  thoroughly  masticated,  addi- 
tional work  is  required  of  the  stomach,  which  is  usually 
an  overworked  organ  because  of  doing  the  work  of  the 
mouth  as  well.  Although  much  of  the  mechanical 
preparation  and  mixing  of  foods  is  of  necessity  done  in 
the  stomach,  some  of  it  may  advantageously  be  done  in 


228       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

the  -mouth.     The  stomach  should  not  be  required  to 
perform  the  function  of  the  gizzard  of  a  fowl. 

237.  Palatability  of  Foods.  —  Many  foods  naturally 
contain  essential  oils  and  other  substances  which  im- 
part palatajgtity.     These  have  but  little  in  the  way  of 
nutritive  value,  but  they  assist  in  rendering  the  nutri- 
ents with  which   they  are  associated  more  digestible. 
Palatability  of  a  food  favorably  influences  the  secretion 
of  the  gastric  and  other  digestive  fluids,  and  in  this  way 
the  natural  flavors  of  well-prepared  foods  aid  in  diges- 
tion.    In  the  feeding  of  farm  animals  it  has  been  found 
that  when  foods  are  consumed  with  a  relish  better  re- 
turns are  secured  than  when  unpalatable  foods  are  fed. 
To  secure  palatability  the  excessive  use  of  condiments 
is  unnecessary.     It  is  possible  to  a  great  extent  during 
preparation  to  develop  and  conserve  the  natural  flavors. 
Some  foods  contain  bitter  principles  which  are  removed 
during  the  cooking,  while  in  others  pleasant  flavors  are 
developed.     Palatability  is  an  important  factor  in  the 
digestibility  of  foods. 

238.  Physiological  Properties  of  Food.  —  Some  food 
materials,    particularly    fruits    and   vegetables,    contain 
compounds  which  have  definite  physiological  properties, 
as   tannin  which   is    an  astringent,  special   oils  which 
exert  a  cathartic  action,  and  the  alkaloids  which  serve 
as  irritants  to  nerve  centers.     Wheat  germ  oil  is  laxa- 
tive, and  it  is  probable  that  the  physiological  properties 
of  graham  and  whole  wheat  breads  are  due  in  some 


THE    DIGESTIBILITY    OF    FOODS  22Q 

degree  to  the  oil  which  they  contain.67  The  use  of 
fruits,  herbs,  and  vegetables  for  medicinal  purposes  is 
based  upon  the  presence  of  compounds  possessing  well- 
defined  medicinal  properties.  As  a  rule  food  plants  do 
not  contain  appreciable  amounts  of  such  substances, 
and  the  use  of  food  for  medicinal  effect  sjiould  be  by 
the  advice  of  a  physician.  The  physiological  proper- 
ties of  some  foods  are  due  to  bacterial  products.  See 
Chapter  XX. 

239.  Individuality.  —  Material  difference  in  digestive 
power  is  noticeable  among  individuals.  Digestion  ex- 
periments show  that  one  person  may  digest  5  per  cent 
more  of  a  nutrient  than  another.  This  difference  ap- 
pears to  be  due  to  a  number  of  factors,  as  activity  of 
the  organs,  as  affected  by  exercise  and  kind  of  labor 
performed ;  abnormal  composition  of  the  digestive 
fluids ;  or  failure  of  the  different  parts  of  the  digestive 
tract  to  act  in  harmony.  Individuality  is  one  of  the 
most  important  factors  in  digestion.  Persons  become 
accustomed  to  certain  foods  through  long  usage,  and 
the  digestive  tract  adapts  itself  to  those  foods,  render- 
ing sudden  and  extreme  changes  in  the  dietary  hazard- 
ous. Common  food  articles  may  fail  to  properly  digest 
in  the  case  of  some  individuals,  while  with  others  they 
are  consumed  with  benefit.  What  is  food  to  one  may 
prove  to  be  a  poison  to  another,  and  while  general 
statements  can  be  made  in  regard  to  the  digestibility  of 
foods,  individual  differences  must  be  recognized. 


ALUE 


230       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

240.  Psychological  Factors.  —  Previously  conceived 
ideas  concerning  foods  influence  digestibility.  Foods 
must  be  consumed  with  a  relish  in  order  to  secure  the 
best  results,  as  flow  of  the  digestive  fluids  and  activity 
of  the  organs  are  to  a  certain  extent  dependent  upon 
the  nerve  centers.  If  it  is  believed  that  a  food  is 
poisonous  or  injurious,  even  when  the  food  is  whole- 
some, normal  digestion  fails .  to  take  place.  In  ex- 
periments by  the  author,  in  which  the  comparative 
digestibility  of  butter  and  oleomargarine  was  being 
studied,  it  was  found  that  when  the  subjects  were  told 
they  were  eating  oleomargarine,  its  digestibility  was  de- 
pressed 5  per  cent,  and  when  they  were  not  told  the 
nature  of  the  material,  but  assumed  that  butter  was 
oleomargarine,  the  digestibility  of  the  butter  was  low- 
ered about  6  per  cent.13  Preconceived  notions  in  regard 
to  foods,  not  founded  upon  well-established  facts,  but 
due  to  prejudice  resulting  from  ignorance,  cause  many 
valuable  foods  to  be  excluded  from  the  dietary.  Many 
persons,  like  the  foreign  lady  who,  visiting  this  country, 
said  she  ate  only  acquaintances,  prefer  foods  that  have 
a  familiar  taste  and  appearance,  and  any  unusual  taste 
or  appearance  detracts  from  the  value  because  of  the 
psychological  influence  upon  digestion. 


CHAPTER   XVI  , 
COMPARATIVE  COST  AND  VALUE  OF  FOODS 

241.  Cost  and  Nutrient  Content  of  Foods. — The  mar- 
ket price  and  the  nutritive  value  of  foods  are  often  at 
variance,  as  those  which  cost  the  most  frequently  con- 
tain the  least  nutrients.75     It  is  difficult  to  make  abso- 
lute comparisons  as  to  the  nutritive  value  of  foods  at 
different  prices,  because   they  differ   not   only  in   the 
amounts,  but  also  in  the  kinds  of  nutrients.     While  it  is 
not  possible  to  express  definitely  the  value  of  one  food 
in  terms  of  another,  approximate  comparisons  may  be 
made  as  to  the  amounts  of  nutrients  that  can   be   se- 
cured for  a  given  sum  of  money  when  foods  are  at  dif- 
ferent prices,  and  tables  have  been  prepared  making 
such  comparisons. 

242.  Nutrients  Procurable  for  a  Given  Sum.7  —  To  as- 
certain the  nutrients  procurable  for  a  given  sum  first 
determine  the  amount  in  pounds  that  can  be  obtained, 
say,  for  ten  cents,  and  then  multiply  by  the  percentages 
of  fat,  protein,  carbohydrates,  and  calories  in  the  food. 
The  results  are  the  amounts,  in  pounds,  of  nutrients 
procurable  for  that  sum  -  of  money.     For  example:   if 

23' 


232        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


: 


.  I<YM)D    AND    DiHT, 

wi  2~H  mi  POSITION  OF  FOOD  MATKKIALS. 

M  THIKMX,  KMirsi;,  AM)  n*KI,  VAM'K. 

M'TlilF.V|>  \ji\M  Ti;iF,vr-  Kl  Y.I  \  U,i  R  • 


10     20     30     40     50     60     70     80     90    10 
400    800    1200   1600  2000  2400  2800  3200  3finn  401 


Codfish,  fresb 

CodMisalt 

Oysters 

Miik 

Butter 


Wheat  bread 
Wheat  fiour 
Corn  meal 
Oatmeal 
Beans,  dried 
Rice 

Potatoes 
Sugar 


FIG.  56.  — COMPOSITION  OF  FOODS. 
(From  Office  of  Experiment  Stations  Bulletin.) 


COMPARATIVE    COST    AND    VALUE    OF    FOODS          233 

milk  is  5  cents  per  quart,  two  quarts  or  approximately 
four  pounds,  can  be  procured  for  10  cents.  If  the  milk 
contain  fat,  4  per  cent,  protein,  3.3  per  cent,  carbo- 
hydrates, 5  per  cent,  and  fuel  value,  310  calories  per 
pound,  multiplying  each  of  these  by  4  gives  the  nutri- 
ents and  fuel  value  in  four  pounds,  or  10  cents  worth 
of  milk,  as  follows: 

Protein 0.13  Ib. 

Fat        . o.i61bi 

Carbohydrates 0.2  Ib. 

Calories 1240 

If  it  is  desired  to  compare  milk  at  5  cents  per  quart 
with  round  steak  at  15  cents  per  pound,  10  cents  will 
procure  0.66,  or  two  thirds  of  a  pound  of  round  steak 
containing  on  an  average  (edible  portion)  19  per  cent 
protein,  12.8  per  cent  fat,  and  yielding  890  calories  per 
pound.  If  10  per  cent  is  refuse,  there  is  edible  about 
0.6  of  a  pound.  The  amounts  of  nutrients  in  the  0.6  of 
a  pound  of  steak,  edible  portion,  or  0.66  Ib.  as  pur- 
chased would  be : 

Protein o.ii  Ib. 

Fat 0.08  Ib. 

Calories 534 

It  is  to  be  observed  that  from  the  10  cents'  worth  of 
milk  a  little  more  protein,  0.08  of  a  pound  more  fat,  and 
nearly  two  and  one  half  times  as  many  calories  can  be 
secured  as  from  the  10  cents'  worth  of  meat.  This  is 
due  to  the  carbohydrates  and  the  larger  amount  of  fat 


234       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

which  the  milk  contains.  At  these  prices,  milk  should 
be  used  liberally  in  the  dietary,  as  it  furnishes  more  of 
all  the  nutrients  than  does  meat.  It  would  not  be  ad- 
visable to  exclude  meat  entirely  from  the  ration,  but 
milk  at  5  cents  per  quart  is  cheaper  food  than  meat  at 
15  cents  per  pound.  In  making  comparisons,  prefer- 
ence cannot  always  be  given  to  one  food  because  of  its 
containing  more  of  any  particular  nutrient,  for  often 
there  are  other  factors  that  influence  the  value. 

243.  Comparing  Foods  as  to  Nutritive  Value. — In 
general,  preference  should  be  given  to  foods  which  sup- 
ply the  most  protein,  provided  the  differences  between 
the  carbohydrates  and  fats  are  not  large.  When  the 
protein  content  of  two  foods  is  nearly  the  same,  but  the 
fats  and  carbohydrates  differ  materially,  the  preference 
may  safely  be  given  to  the  food  which  supplies  the 
larger  amount  of  total  nutrients.  A  pound  of  protein 
in  a  ration  is  more  valuable  than  a  pound  of  either  fat 
or  carbohydrates,  although  it  is  not  possible  to  establish 
an  absolute  scale  as  to  the  comparative  value  of  these 
nutrients,  because  they  serve  different  functional  pur- 
poses in  the  body.  It  is  sometimes  necessary  to  use 
small  amounts  of  foods  rich  in  protein  in  order  to  se- 
cure a  balanced  ration ;  excessive  use  of  protein,  how- 
ever, is  not  economical,  as  that  which  is  not  needed  for 
functional  purposes  is  converted  into  heat  and  energy 
which  could  be  supplied  as  well  by  the  carbohydrates, 
and  they  are  less  expensive  nutrients. 


FOOD    AM)    DIET. 

(luu-CS—  raTM.VKY  KCOXHMY  OF  F 


Amounts  of  Nutrients.  Ohtiminl  in   DHfVivnf    l*'o«i|   .Mjit<>ri;tl»  for  IO  mils. 

1'n.fHn.  K;iK    .          <  ui-lM,ti\ilriit.-x  t'u,.|  Xi,|,,,,,  Miii.Tiil 


lib.       ZLk      3Lbs.      4Lbs. 


Beet  round  12  ,83  mm 

Beef,  sirloin  18  ,55  — 

Beef,  rib  16  .63  mm 

Mutton,  leg  12  ,83  JL 

Pork,  spare  rib  12  .83  mm 

Pork,  salt  fat  14  ,71 

Ham  smoked  16  .63 

Codfish,  fresh  8  125, 

Codfish,  salt  6  167  • 

Oysters.  40  ct&qt  20  .501 

lilk.6cteqt  3  3.33  « 

Butter  24  ,42  S 

Cheese  16  .63  J 

o-s.  25  ets.  doz,  16!  ,60.  i 

Wheat  bread  4  2,50  — 
Wheat  flour 

Cora  meal  2  5,00 

Oatoeal  4  2.50 

Beans,  white,  dried  4  2.50 

Rice  5  2,00  - 

Potato.  60  cts.  bush,    1  10.00 

Sugar  5  2.00 


FIG.  57. — PECUNIARY  ECONOMY  OF  FOOD. 

(From  Office  of  Experiment  Stations  Bulletin.) 

235 


236       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


TEN  CENTS  WILL  PURCHASE  : 

(From  Farmer's  Bulletin  No.  142,  U.  S.  Dept.  of  Agr.) 


KIND  OF  FOOD  MATERIAL 

PRICE 

PER 

POUND 

TOTAL 
WEIGHT 
OF  FOOD 
MATE- 
RIAL 

PRO- 
TEIN 

FAT 

CAR- 
BOHY- 
DRATES 

ENERGY 

Beef,  sirloin     

Cents 

25 

Pounds 
0.40 

Pound 
O.o6 

Pound 
0.06 

Pounds 

Calories 
410 

Do  

20 

0.50 

0.08 

0.08 

CIC 

Do  

15 

0.67 

O.IO 

O.II 

68  c 

16 

0.63 

o.n 

o  08 

VJU^J 

c6o 

Do  

14 

O  71 

O  I  "3 

O  OQ 

630 

Do  

12 

0.8q 

0.  1C 

O.IO 

74.O 

Beef,  shoulder  clod      .... 
Do  

12 

9 

o  83 

I.  II 

0.13 

0.18 

0.08 

O.IO 

— 

595 

7QC 

Beef  stew  meat            .... 

5 

2  OO 

O  2Q 

O  23 

jroo 

Beef,  dried,  chipped     .... 
Mutton  chops  loin  

11 

0.40 

o  63 

O.IO 
O.O8 

O.O3 
O  17 

— 

315 

890 

Mutton,  leg     

20 

0.50 

O.O7 

O.O7 

A  A  e 

Do  

16 

o  63 

O.OO 

o  09 

^•-p 
c6o 

Roast  pork,  loin      

12 

0.83 

O.II 

O.I9 

IO3C 

Pork,  smoked  ham      .... 
Do  

22 

18 

0.45 

0.56 

0.06 
0.08 

0.14 

0.18 

— 

735 
QIC 

Pork  fat  salt  

12 

o  8q 

O.O2 

0.68 

2Q  CO 

Codfish,  dressed,  fresh     .     .     . 
Halibut  fresh      ...          .     . 

10 

18 

I.OO 

o  c6 

O.II 
0.08 

O.O2 

— 

22O 

26C 

Cod,  salt     

7 

1.43 

O.22 

O.OI 

•«O 

465 

Mackerel,  salt,  dressed    .    .     . 
Salmon,  canned  

10 
12 

I.OO 

0.83 

O.I3 

0.18 

O.2O 
O.IO 

— 

H35 
760 

Oysters,  solids,  50  cents  per  quart 
Oysters,  solids,  35  cents  per  quart 
Lobster,  canned      

25 

18 
18 

0.40 
0.56 
o.c6 

0.02 

0.03 

O.IO 

O.OI 
O  OI 

O.OI 
0.02 

90 

125 
22C 

Butter    

20 

0.50 

O.OI 

0.40 

I7CC 

Do  

25 

0.40 

0.32 

iq6c 

Do  

30 

0.33 

0.27 

II2C 

Eggs,  36  cents  per  dozen      .     . 
Eggs,  24  cents  per  dozen      .     . 
Eggs,  12  cents  per  dozen      .     . 
Cheese  ...                   .          . 

24 

16 
8 
16 

0.42 
0.63 

1-25 
o  63 

0.05 
0.07 
0.14 
0.16 

0.04 
0.06 

O.II 
O.2O 

O.O2 

260 

385 
770 
Il85 

Milk,  7  cents  per  quart    .     .     . 
Milk,  6  cents  per  quart     .     .     . 
Wheat  flour    

3^ 
3 
3 

2.85 

3-33 
3-33 

0.09 

O.II 

0.32 

O.II 
O.I3 
O.O3 

O.I4 
O.I7 
2.45 

885 
1030 
C44O 

Do  

2k 

4.00 

O.QQ 

O.O4 

2.94 

6540 

Corn  meal,  granular    .... 
Wheat  breakfast  food      .     .     . 
Oat  breakfast  food  

*\ 

n 

7k 

4.00 

1-33 

1.33 

0.31 
0.13 

0.19 

0.07 
0.02 
O.O9 

2.96 
0.98 

0.86 

6540 

2235 
2395 

Oatmeal     

4 

2.  CO 

O.^vj. 

0.16 

1.66 

4500 

Rice  

8 

I.2C 

0.08 

0.97 

2025 

^Vheat  bread  

6 

1.6? 

0.13 

O.O2 

0.87 

2OOO 

Do  

5 

2.OO 

0.16 

O.O2 

1.04 

2400 

Do  

4 

2  CO 

O.2O 

0.03 

1.30 

3OOO 

Rye  bread  

5 

2.OO 

0.15 

O  Ol 

1.04 

2340 

Beans,  white,  dried      .... 

5 

2.00 

0.35 

0.03 

1.16 

3040 

COMPARATIVE  COST  AND  VALUE  OF  FOODS 


237 


KIND  OF  FOOD  MATERIAL 

PRICE 

PER 

POUND 

TOTAL 
WEIGHT 
OF  FOOD 
MATE- 
RIAL 

PRO- 
TEIN 

FAT 

CAR- 
BOHY- 
DRATES 

ENERGY 

Cabbage     . 

25 

4.  oo 

O  Os 

O  OI 

o  18 

4.60 

Celery    

5 

2.OO 

O.O2 

o  05 

TOO 

Corn,  canned      ...         .     . 

10 

I  OO 

O  O2 

O  OI 

o  18 

A3O 

Potatoes,  90  cents  per  bushel  . 
Potatoes,  60  cents  per  bushel  . 
Potatoes,  45  cents  per  bushel   . 
Turnips  

li 

i 

3 

i 

6.67 

10.  OO 

13-33 

IO  OO 

0.10 
0.15 
0.20 

o  08 

0.01 
O.OI 
0.01 
O  OI 

°-93 
1.40 
1.87 

O  £4. 

1970 
2950 

3935 
1  200 

Apples   

ii 

6.67 

O  O2 

o  02 

o  65 

1270 

Bananas      

7 

I  43 

O  OI 

O  OI 

o  18 

Q7O 

Oranges      

6 

1.67 

O  OT 

O  13 

o  CO 

Strawberries   .... 

7 

I  4.3 

OI 

O  OI 

O  OQ 

OTC 

Sugar     

6 

I  67 

I  67 

^•"o 

292O 

It  is  to  be  noted  in  the  table  that,  ordinarily,  for  the 
same  amount  of  money  the  most  nutrients  can  be  ob- 
tained in  the  form  of  milk,  cheese,  sugar,  and  beans,  corn 
meal,  wheat  flour,  oatmeal,  and  cereals  in  bulk.  While 
meats  supply  protein  liberally,  they  fail  to  furnish  car- 
bohydrates as  the  vegetables.  As  discussed  in  the 
chapter  on  Dietary  Studies  of  Families,  unnecessarily 
expensive  foods  are  often  used,  resulting  either  in  lack 
of  nutrients  or  unbalanced  rations. 

EXAMPLES 

1.  Compute  the  calories  and  the  amounts  of  protein,  fat,  and  car- 
bohydrates that  can  be  procured  for  25   cents  in  cheese  selling  for 
1 8  cents  per  pound ;   how  do  these  compare  with  the  nutrients  in 
eggs  at  20  cents  per  dozen  ? 

2.  Which  food  furnishes  the  larger  amount  of  nutrients,  potatoes 
at  50  cents  per  bushel  or  flour  at  $6  per  barrel  ? 

3.  How  do  beans  at  10  cents  per  quart  compare  in  nutritive  value 
with  beef  at  15  cents  per  pound  ? 

4.  How  does  salt  codfish  at  10  cents  per  pound  compare  in  nu- 
tritive value  with  lamb  chops  at  15  cents  per  pound  ? 

5.  Compare  in  nutritive  value  cream  at  25   cents  per  quart  with 
butter  at  30  cents  per  pound. 

6.  Calculate  the  composition  and  nutritive  value  of  a  cake  made 
of  sugar,  8  oz. ;  butter,  4  oz. ;    eggs,  8  oz. ;    flour,  8  oz. ;  and  milk, 
4  oz. ;  the  baked  cake  weighs  one  and  three  fourths  pounds. 


238        HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 


AVERAGE   COMPOSITION  OF    COMMON   AMERICAN  FOOD 
PRODUCTS 

(From  Farmer's  Bulletin,  No.  142,  U.  S.  Dept.  of  Agr.) 


FOOD  MATERIALS  (as  purchased) 

REFUSE 

WATER 

PROTEIN 

1 

CARBO- 
HYDRATES 

tt 
«? 

FUEL  VALUE 
PER  POUND 

ANIMAL  FOOD 

Beef,  fresh  : 
Chuck  ribs  

% 
16  Q 

% 

Co  6 

% 

JC    C 

% 

ic  o 

% 

%    . 

o  8 

Calo- 
ries 

QIO 

Flank  .      . 

IO  2 

c/i  o 

17  O 

IQ  O 

O  7 

IIO5 

Loin  

10  o. 

C2  C 

16  i 

17   C. 

O.Q 

IO2C, 

Porterhouse  steak 

12  7 

52  4 

TQ  T 

17  Q 

0  8 

IIOO 

Sirloin  steak  

12  8 

CA    O 

16  c 

16  i 

0.9 

07  c 

Neck  

27  6 

,1C    Q 

14  C. 

II  Q 

O  7 

V/D 
HOC 

Ribs  

20  8 

4.0  8 

10.  Q 

21   2 

0.7 

nqc, 

Rib  rolls  

*JO'° 

6q   Q 

IQ  °. 

16  7 

O  Q 

IOCC 

Round  

7  2 

60.7 

IQ.O 

12  8 

I.O 

890 

Rump  

2O  7 

AC  O 

13  8 

2O  2 

O  7 

IOQO 

Shank,  fore  

q6  Q 

42  Q 

12  8 

7.0 

06 

545 

Shoulder  and  clod 

16  4 

«;6  8 

16  4 

Q  8 

O  Q 

7ic 

Fore  quarter  

18  7 

4Q.I 

14  c 

17.  c 

0.7 

995 

Hind  quarter 

1C  7 

co  4. 

ic  4. 

18  3 

O  7 

IO4C 

Beef,  corned,  canned,  pickled,  dried  : 
Corned  beef 

8  4 

4Q  2 

14  °. 

23  8 

4  6 

124  £ 

Tongue,  pickled  

60 

c8.Q 

II.  Q 

19.2 

4-3 

IOIO 

Dried  salted  and  smoked 

4  7 

cq  7 

ii.y 

2O  4 

6  Q 

8.9 

7QO 

Canned  boiled  beef 

C.I  8 

2C  c 

22  £. 

i  3 

I4IO 

Canned  corned  beef  

^J-.O 

t;i  8 

*$•:> 

26  3 

*JC.ij 

18  7 

4.O 

I27O 

Veal: 
Breast  

21  Q 

Co  O 

ic  4. 

II  O 

0.8 

74^ 

Leg  

14.2 

60.  1 

ICC 

7-9 

0.9 

f* 

625 

Leg  cutlets  

q  4. 

68  q 

2O  I 

7  c 

I.O 

69  c, 

24.  C 

C.4.2 

1C.  I 

6.0 

0.7 

535 

Hind  quarter  

2O  7 

~>7 

CQ  2 

* 

IO  2 

6.6 

0.8 

580 

Mutton  : 
Flank  

Q  Q 

OQ  o 

iq  8 

q6.Q 

0.6 

1770 

18.4 

C.I.2 

1C.  I 

14.7 

. 

0.8 

890 

Loin  chops  

16  o 

42  o 

iq.c 

28.  Q 

0.7 

1415 

Fore  quarter 

21  2 

41  6 

12  Q 

24  £, 

o  7 

I2QC. 

Hind  quarter,  without  tallow  
Lamb: 
Breast  

I7.2 
I9.I 

45-4 

4.C.C 

13-8 
ic.  4 

23.2 
IQ.I 

— 

0.7 
0.8 

1210 
107? 

Leg   hind  

17  4 

C2.Q 

ICQ 

iq.6 

0.9 

86^ 

COMPARATIVE    COST    AND    VALUE    OF    FOODS 


239 


AVERAGE  COMPOSITION  OF  COMMON  AMERICAN  FOOD 
PRODUCTS  —  Continued 


FOOD  MATERIALS  (as  purchased) 

REFUSE 

WATER 

PROTEIN 

a 

CARBO- 
HYDRATES 

g 
e/) 

<: 

FUEL  VALUE 
PER  POUND 

ANIMAL  FOOD  —  continued 

Pork,  fresh  : 
Ham  

% 

IO  7 

% 
48  o 

% 
iq.c 

% 

2C  Q 

% 

% 

o  8 

Calo- 
ries 
iq2o 

Loin  chops  

19.7 

41.8 

13.4 

24.2 

0.8 

124^ 

Shoulder  . 

12  4 

44..  Q 

12  O 

20  8 

O  7 

14^0 

Tenderloin  

66.  c 

18.9 

iq.o 

I.O 

89  q 

Pork,  salted,  cured,  pickled  : 
Ham  smoked  

13.6 

34.8 

14.2 

3q.4. 

4.2 

l6qC 

Shoulder    smoked 

18  2 

1,6  8 

iq  O 

26  6 

c  c 

iqqc 

Salt  pork  

7-9 

1.9 

86.2 

q.O 

qccc 

Bacon  smoked 

7  7 

17  4 

91 

62  2 

4  I 

27TC 

Sausage  : 
Bologna  

q  q 

55.2 

18.2 

19.7 

3.8 

lice 

Pork  

on  8 

iq  o 

44  2 

I  i 

2.2 

2O7C, 

Frankfort  



C-7.2 

J.J.W 
19.6 

18.6 

i.i 

q.4 

lice 

Soups  : 
Celery,  cream  of  

88.6 

2.1 

2.8 

r  O 

I.c 

2qC 

Beef  

Q2  Q 

4  4 

O  4 

I  I 

I  2 

1  2O 

Meat  stew  

84  <; 

4.6 

4..q 

5c 

I.I 

q6q 

Tomato  

90.0 

1.8 

I.I 

5.6 

1.5 

IS? 

Poultry  : 
Chicken,  broilers  

41.6 

43-7 

12.8 

1-4 

0.7 

°/x 

Fowls  

2C  Q 

47.1 

iq  7 

12  q 

O  7 

O^D 
76  C 

Goose  

17  6 

•38  c. 

jq  4 

20  8 

O  7 

147  C 

22  7 

42.4 

16  i 

18  4 

0.8 

lOOO 

Fish  : 
Cod,  dressed  

2Q  Q 

cR  c 

II  I 

O  2 

0.8 

22O 

Halibut  steaks  or  sections 

17  7 

6l  Q 

ic  q 

4      A 

o  o 

4.7  cJ 

Mackerel,  whole  

44.7 

4O  4 

IO  2 

4  2 

0.7 

q7O 

Perch,  yellow  dressed. 

qc  i 

CQ  7 

12  8 

O  7 

O  Q 

27  C 

Shad,  whole  

C.O.  I 

qc.2 

9.4 

4  8 

0.7 

q8o 

71.2 

2O  Q 

q  8 

2  6 

I.c 

3*»w 

6OO 

Fish,  preserved: 
Cod,  salt  

24  Q 

4O  2 

16  o 

O  4 

i8.q 

q2C 

Herring    smoked 

44  4 

TQ   2 

20  c. 

8  8 

7  J. 

7CC 

Fish,  canned  

Salmon  

60  e 

21  8 

12  I 

2  6 

QIC 

Sardines  

*q.o 

^5-5 
cq.  6 

2q.7 

12.  1 

e.q 

QCQ 

*  Refuse,  oil. 


240       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


AVERAGE  COMPOSITION  OF  COMMON  AMERICAN  FOOD 
PRODUCTS  —  Continued 


FOOD  MATERIALS  (as  purchased) 

REFUSE 

WATER 

g 

• 

PL. 

fe 

CARBO- 
HYDRATES 

SB 
< 

FUEL  VALUE 
PER  POUND  1 

ANIMAL  FOOD  —  continued 

Shellfish  : 
Oysters    solids  

% 

% 
88  3 

% 

6  o 

% 
I  q 

% 
q  q 

%. 

I  i 

Calo 
ries 

22 

Clams  

1     _ 

80  8 

10  6 

I  i 

52 

2  q 

q4< 

Crabs  

52  A 

36  7 

7  Q 

O  Q 

0  6 

I  e 

2<> 

Lobsters 

6l  7 

on  7 

e  Q 

O  7 

O  2 

o  8 

11 

Eggs  :  Hen's  eggs  

*        ' 
*II  2 

6s  < 

iq  I 

93 

O  Q 

i* 

6q 

Dairy  products,  etc.  : 
Butter  

II  O 

I  O 

85  o 

q  n 

q4K 

Whole  milk  

87  o 

q  q 

4.  O 

tr.o 

O  7 

3K 

Skim  milk  

QO  t? 

34 

o  q 

SI 

O  7 

16 

Buttermilk  

QI.O 
"*•** 

q  o 

O  tJ 

4.8 

O.7 

i6< 

Condensed  milk  

2O  Q 

88 

8  3 

^4  I 

I  Q 

14  V 

Cream  

74.  0 

2  t; 

«•* 

18.1; 

4.e 

o.c 

86 

Cheese,  Cheddar  

27  4 

27  7 

•^6  8 

4  I 

4  o 

207 

Cheese,  full  cream  

q4.2 

2C.Q 

qq,7 

2.4 

q..8 

i88« 

VEGETABLE  FOOD 

Flour,  meal,  etc.  : 
Entire  wheat  flour  

II.  A. 

13.8 

I.O 

71.9 

I.O 

i6« 

Graham  flour  

II  q 

iq.q 

2.2 

71.4 

1.8 

x^v 

164^ 

Wheat  flour,  patent  roller  process 
High-grade  and  medium 

12  O 

II  4 

I  O 

7^  I 

o  ^ 

i6qc 

Low  grade  

12.  0 

14.0 

I.O 

71.2 

0.9 

^a- 

i64C 

IO  3 

iq  4. 

O  Q 

74.1 

i  3 

164^ 

\Vheat  breakfast  food 

0  6 

12  I 

i  8 

7C  2 

i  3 

i63c 

Buckwheat  flour  

iq  6 

64 

1.2 

77.  0 

O.Q 

i6oc 

Rye  flour 

12  Q 

68 

O  Q 

78  7 

O  7 

l62C 

12  C 

O  2 

I  O 

<7t?  4 

I  O 

i6qc 

Oat  breakfast  food  

7.7 

16*7 

7-3 

6X1 

2.1 

i8oc 

R"fte.  .;  '.  

12.  q 

8*0 

O.q 

79.O 

O.4 

1620 

II-4 

0.4 

O.I 

88.0 

O.I 

1650 

Starch  

90.0 

1675 

Bread,  pastry,  etc.  : 
White  bread  

or.  q 

Q.2 

1.3 

53.1 

I.I 

I2OC 

Brown  bread  

AO   6 

e.4 

1.8 

47.1 

2.1 

1040 

••  Refuse,  shell. 


COMPARATIVE    COST   AND    VALUE    OF    FOODS 


241 


AVERAGE  COMPOSITION  OF  COMMON  AMERICAN  FOOD 
PRODUCTS  —  Continued 


FOOD  MATERIALS  (as  purchased) 

REFUSE 

WATER 

PROTEIN 

£ 

6  B 

X 

Cfl 

< 

FUEL  VALUE 
PER  POUND 

VEGETABLE  FOOD  —  continued 

Bread,  pastry,  etc.  : 
Graham  bread                    

% 

qc  7 

% 

8  Q 

% 
i  8 

% 

£2  I 

% 

Calo- 
ries 

HOC. 

\Vhole  wheat  bread 

qg  A 

O  7 

'5 

HqO 

Rye  bread  

qt  7 

9O 

o  6 

rq  2 

j'l 

1170 

Cake  

IQ  Q 

6.q 

Q.O 

63  3 

j*^ 

1630 

Cream  crackers  

6  8 

Q  7 

12  I 

60  7 

I  7 

TQ2C 

4.8 

zo.c; 

7O  ^ 

2  Q 

IQIO 

Soda  crackers  

e  Q 

Q  8 

91 

2  I 

I87C 

Sugars,  etc.  : 
Molasses  

70  o 

122^ 

Candy  *  

96  o 

1680 

Honey 

81  o 

I42O 

IOO  O 

I7CO 

Maple  sirup             .....      . 

71  A 

12^0 

Vegetables  :  f 

12  6 

22  C, 

i  8 

CQ  6 

o  t 

1C,  20 

Beans  Lima  shelled  

68  5 

O  7 

22  O 

C  AQ 

7  O 

8q  o 

2  I 

O  3 

6  Q 

O  7 

1  70 

Beets  

2O  O 

70  o 

O  I 

7  7 

O  Q 

1  60 

Cabbage  

It  o 

77  7 

I  4. 

O.2 

V* 

O  Q 

Celery.  

20  o 

7S  6 

O  Q 

O  I 

2  6 

o  8 

fe 

Corn,  green  (sweet)  ,  edible  portion 
Cucumbers  

TC   O 

75-4 
81  i 

O  7 

I.I 
O  2 

19.7 

2  6 

0.7 

O  4. 

440 

5< 

1C  o 

80  q 

I.O 

O.2 

2.C 

o  8 

s 

Mushrooms  

88  i 

q  £ 

O  4. 

68 

I  2 

185 

IO.O 

1.4 

O.Q 

8.Q 

o.c 

IQO 

Parsnips  

20  o 

664 

O  4. 

10  8 

I  I 

2qo 

Peas  (Pisum  sativum),  dried  
Peas  \Pisum  sativum),  shelled.  .  .  . 
Cowpeas  dried  

9-5 
74.6 

iq  o 

24.6 
7.0 

21  4. 

I.O 
I  A. 

62.0 
16.9 
60  8 

2.9 
I.O 
q  j. 

1565 
440 
irnc; 

2O  O 

62.6 

1.8 

O.I 

14.  ..7 

08 

2QC 

*  Plain  confectionery  not  containing  nuts,  fruit,  or  chocolate. 

fSuch  vegetables  as  potatoes,  squash,  beets,  etc.,  have  a  certain  amount  of  inedible 
material,  skin,  seeds,  etc.  The  amount  varies  with  the  method  of  preparing  the  vege- 
tables, and  cannot  be  accurately  estimated.  The  figures  given  for  refuse  of  vegetables, 
fruits,  etc.,  are  assumed  to  represent  approximately  the  amount  of  refuse  in  these  foods 
as  ordinarily  prepared. 


242       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


iLUE 


AVERAGE  COMPOSITION  OF  COMMON  AMERICAN  FOOD 
PRODUCTS  —  Continued 


H 

M 

SB 

,  8 

8  t? 

as 

i! 

M 
K 

£ 

M 

PH 

fc 

°s 

^ 

H 

VEGETABLE  FOOD  —  continued 

Vegetables  : 
Rhubarb 

4.O  O 

56  6 

O  4. 

O  4. 

2  2 

O  4. 

Calo- 
ries 
(So 

Sweet  potatoes  

2O  O 

CC  2 

0.6 

21-9 

O  Q 

440 

Spinach  .                               

Q2  q 

2  I 

O  q 

q  2 

2  I 

QC 

CQ.O 

44..  2 

O.2 

4.C 

0.4 

IOC 

Tomatoes  

O  Q 

O  4. 

q.n 

O  C. 

IOC 

Turnips 

qo  o 

62  7 

O  Q 

O  I 

c  7 

o  6 

1  20 

Vegetables,  canned  : 
Baked  beans 

68  9 

6  Q 

2  C. 

IQ  6 

2  I 

ccc 

Peas  (Pisum  sativum},  green  .... 
Corn  green  .    .                   .    ' 

— 

85.3 
76  i 

3-6 

2  8 

0.2 
I  2 

9.8 

IQ  O 

I.I 
O  Q 

235 

Succotash 

7C.  Q 

q  6 

I  O 

18  6 

O  O 

A<2  C 

Tomatoes  

Q4,  O 

I  2 

O  2 

4.  O 

o  6 

QT 

Fruits,  berries,  etc.,  fresh  :  * 
Annies  .  . 

2C.  O 

O  3~ 

O  3 

10  8 

O  3 

IOC 

Bananas 

oC  o 

48  Q 

o  8 

O  A 

14.  q 

o  6 

26c 

Grapes  

2C  O 

58  o 

I  O 

I  2 

14  4. 

O  4. 

2QC 

Lemons 

qo  o 

62  5 

O  7 

o  c: 

C   Q 

O  4. 

TOC 

Muskmelons  

CQ  O 

A  \  8 

O  3 

46 

O  3 

8r 

Oranges 

27  O 

6q  4 

o  6 

O  I 

8  15 

O  4 

TCr 

IO  O 

76.O 

o.c 

O.4 

12.7 

O  4. 

2^C 

Persimmons  edible  portion  

66  i 

o  8 

o  7 

qi  c 

O  Q 

ccr 

Raspberries 

85  8 

I  O 

12  6 

»0  6 

2?C 

Strawberries  

C  o 

8c.  Q 

O  Q 

o  6 

7  O 

06 

\Vatermelons            .      .  . 

CQ    A 

q7  c 

O  2 

O  I 

2  7 

O  I 

rr 

Fruits,  dried  : 
Apples  ... 

28  I 

i  6 

2  2 

66  i 

2  O 

20  4 

4.7 

I.O 

62  c. 

2  4. 

JI2* 

Dates  

IO  O 

13  8 

I  Q 

2  C. 

7O  6 

I  2 

I27C 

*  Fruits  contain  a  certain  proportion  of  inedible  materials,  as  skin,  seeds,  etc.,  which 
are  properly  classed  as  refuse.  In  some  fruits,  as  oranges  and  prunes,  the  amount 
rejected  in  eating  is  practically  the  same  as  refuse.  In  others,  as  apples  and  pears, 
more  or  less  of  the  edible  material  is  ordinarily  rejected  with  the  skin  and  seeds  and 
other  inedible  portions.  The  edible  material  which  is  thus  thrown  away,  and  should 
properly  be  classed  with  the  waste,  is  here  classed  with  the  refuse.  The  figures  for 
refuse  here  given  represent,  as  nearly  as  can  be  ascertained,  the  quantities  ordinarily 
rejected. 


COMPARATIVE  COST  AND  VALUE  OF  FOODS 


243 


AVERAGE  COMPOSITION  OF  COMMON  AMERICAN  FOOD 
PRODUCTS  —  Continued 


FOOD  MATERIALS  (as  purchased) 

REFUSE 

M 
M 

H 

< 

PROTEIN 

fe 

CARBO- 
HYDRATES 

K 

W3 

<5 

FUEL  VALUE 
PER  POUND 

VEGETABLE  FOOD  —  continued 

Fruits,  dried: 
Figs  .  .  , 

% 

% 

18  8 

% 

4.  "3 

% 
O  3 

% 

74.  2 

% 

2  4. 

Calo- 
ries 

1280 

Raisins  

10  o 

iq  T 

2  Q 

Q  O 

68  5 

3T 

126^ 

Nuts: 
Almonds  

jr  o 

2  7 

II   £ 

qo  2 

o  c 

-1 
j   j 

ICIC 

Brazil  nuts  

45  -^ 

AQ   O 

2.6 

8  6 

qq  7 

3C 

2  O 

1515 

14.8^ 

Butternuts  

86  4. 

o  6 

3  8 

8  Q 

o  c 

O  A. 

qgC 

Chestnuts  fresh 

16  o 

Q7  8 

52 

4.  C 

OCA 

j   j 

o°5 

9T  r 

Chestnuts   dried  

24  o 

A  e 

8  i 

e  q 

35-4 

^6  4. 

I  7 

X5 

rqgi- 

Cocoanuts  

*48.8 

7.2 

2  Q 

2C  Q 

14.  ^ 

O  O 

I2Q< 

Cocoanut,  prepared  .    . 

q  e 

6  3 

ry  ,< 

3T    t 

I  Q 

2865 

Filberts   . 

to   I 

i  8 

7   £ 

qr   q 

i*5 

6  2 

j   j 

IAQO 

Hickory  nuts  

62  2 

I  4. 

«;  8 

2C   C 

4.  Q 

o  8 

I  IJ.^ 

Pecans  polished 

rq  2 

I  A 

50 

qq  q 

6  2 

O  7 

T  A  At 

Peanuts  

24.  c 

6  Q 

TQ   t 

2Q  I 

18  c 

T  e 

177  1 

Pinon  {Pinus  edulis) 

40  6 

2  O 

8  7 

36  8 

JO  2 

I  7 

17  3O 

Walnuts  black  

74.  I 

o  6 

7  2 

14.  6 

q  o 

O  ^ 

7qO 

\Valnuts  English. 

<;8  i 

I  O 

6  Q 

26  6 

6  8 

o  6 

J2CQ 

Miscellaneous  : 
Chocolate  

r  Q 

12  Q 

48  7 

qo  q 

2  2 

C62CJ 

Cocoa,  powdered  

16 

21  6 

28.Q 

qy  7 

7  2 

2160 

Cereal   coffee,   infusion    (i   part 
boiled  in  20  parts  water)"!" 

08  2 

O  2 

I  4. 

O  2 

qn 

*  Milk  and  shell. 

t  The  average  of  five  analyses  of  cereal  coffee  grain  is  :  Water  6.2,  protein  13.3,  fat 
3.4,  carbohydrates  72.6,  and  ash  4.5  per  cent.  Only  a  portion  of  the  nutrients,  however, 
enter  into  the  infusion.  The  average  in  the  table  represents  the  available  nutrients  in  the 
beverage.  Infusions  of  genuine  coffee  and  of  tea  like  the  above  contain  practically  no 
nutrients. 


CHAPTER   XVII 
DIETARY  STUDIES 


244.  Object  of  Dietary  Studies.  —  The  quantity  of  food 
which  different  families  purchase  varies  between  wide 
limits ;  a  portion  being  lost  mechanically  in  preparation 
and  a  still  larger  and  more  variable  amount  in  the  ref- 
use and  non-edible  parts.     If  a  record  is  made  of  all 
foods  purchased  and  the  waste  and  non-edible  portions 
are  deducted,  the  nutrients  consumed  by  a  family  may 
be  calculated  by  multiplying  the  weight  of  each  food 
by  the  average  composition.     If  such  calculations  be 
made,  it  will  be  found  that  in  some  families  nearly  a 
half  pound  per  day  of  both  protein  and  fat  is  consumed 
by  adults,  while  in  other  families  less  than  half  of  this 
amount  is  used.     The  object  of  dietary  studies  is  to  de- 
termine the  source,  cost,  composition,  and  nutritive  value 
of  the  foods  consumed  by  different  families;  they  also 
enable  comparisons  to  be  made  of  the  amounts  of  nu- 
trients purchased.     Extensive  dietary  studies  have  been 
made  by  the  United  States  Department  of  Agriculture, 
and  the  results  have  been  published  in  various  bulletins.76 

245.  Wide  and  Narrow  Rations.  —  When  the  amount 
of  carbohydrates  in  a  ration  is  small  in  comparison  with 
the  protein,  it  is  called  a  narrow  ration,  while  a  wide 
ration  is  one  in  which  the  carbohydrates  are  much  in  ex- 

244 


DIETARY    STUDIES  245 

cess  of  the  protein.  When  a  ration  contains  0.40  of  a 
pound  of  protein,  0.40  of  a  pound  of  fat,  and  i  pound  of 
carbohydrates,  it  has  a  nutritive  ratio  of  i  to  4.8  and  is 
a  narrow  ration.  To  calculate  the  nutritive  ratio,  the 
fat  is  multiplied  by  2^,  the  product  added  to  the 
carbohydrates,  and  this  sum  divided  by  the  protein. 
It  is  not  possible  to  designate  accurately  the  amount 
of  protein  and  other  nutrients  that  should  be  in  the 
daily  ration  of  all  persons,  because  the  needs  of  the 
body  vary  so  with  different  individuals.  Hard  and  fast 
rules  governing  the  amounts  of  nutrients  to  be  consumed 
cannot  as  yet  be  formulated,  as  our  knowledge  of  the 
subject  is  too  limited.  It  is  known  that  both  excessive 
and  scant  amounts  are  alike  injurious.  While  the  appe- 
tite may  indicate  either  hunger  or  satiety,  it  alone  can- 
not always  be  relied  upon  as  a  safe  guide  for  determining 
the  amount  and  kind  of  food  to  consume,  although  the 
demands  of  appetite  should  not  be  disregarded  until  it 
has  been  demonstrated  beyond  a  doubt  that  it  is  not 
voicing  the  needs  of  nature.  There  has  been  a  tendency 
which  perhaps  was  a  survival  of  the  Puritanical  ideas 
of  the  early  days  to  stamp  as  hurtful  whatever  seemed 
desirable  and  pleasant ;  as  examples  might  be  cited  the 
craving  for  water  by  fever  patients,  and  for  sugar  by 
growing  children,  which  have  now  been  proven  to  be 
normal  demands  of  nature. 

246.   Dietary  Standards.  —  As  a  result  of  a  large  num- 
ber of  dietary  studies  and  digestion  experiments,  dietary 


246        HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

standards  have  been  prepared.  Atwater  in  this  coun- 
try and  Voit  in  Germany  have  proposed  such  standards 
for  men  employed  at  different  kinds  of  labor,  as  follows  : 


8 

h 

B    « 

J    W 

U     ts 

M 
p 

& 

£ 

§    < 

II 

8 
S5 

Ib. 

Ib. 

Ib. 

Calories 

Ratio 

Man  with  little  physical  exercise    . 

0.20 

O.2O 

0.66 

2450 

5-5 

Man  with  ligh  ::  muscular  work  .     . 

O.22 

O.22 

0.77 

280O 

5-7 

Man  with  moderate  muscular  work 

0.28 

0.28 

0.99 

3520 

5.8 

Man  with  active  muscular  work  . 

0.33 

°-33 

1.  10 

4000 

5.6 

Man  with  hard  muscular  work  .     . 

°-39 

0.55 

1-43 

5700 

6.9 

In  the  table  it  will  be  seen  that  the  quantity  of  nu- 
trients increases  with  the  labor  to  be  performed.  In 
order  to  secure  the  necessary  heat  and  energy,  rations 
for  men  at  heavy  labor  contain  proportionally  more 
fat  and  carbohydrates  than  are  required  for  light  work. 
All  dietary  standards,  however,  should  be  regarded  as 
tentative  only.  Opinions  differ  greatly  on  different 
points ;  for  example,  as  to  the  amount  of  protein  a  ration 
should  contain.  This  is  a  matter  that  can  be  deter- 
mined only  from  extended  investigations  under  a  variety 
of  conditions,  and  as  yet  results  are  too  meager  to  for- 
mulate other  than  tentative  standards.  Chittenden  has 
found  that  the  body  can  be  sustained  on  very  much 
less  protein  than  is  called  for  in  the  standard  ration.77 
The  amount  of  protein  in  the  ration  should  be  ample 
to  sustain  the  body  weight  and  maintain  a  nitrogen 


FOOD    AM)    DIET. 

Chm-i  4.— DIKTA1I1KS  AM)  DIKTAKV  STAM>AI!DS. 


!Lb.       ZLbsL      3  UK, 
2000  Cal  4000  Gal  6000  Cal. 


Underfed  laborers,  Italy 
Students,  Japan 
Lawyer,  Germany 
Physician.  Germany 
Physician.  Denmark 
Well-fed  tailor.  England 
Laborers  at  active  work.  England 
Well-paid  mechanics.  Germany 
Miners  at  severe  work.  Prussia 
Mechanics  at  moderate  work.  Sweden 
Mechanics  at  severe  work.  Sweden 
Chemist.  Connecticut 
College  professor.  Connecticut 
College  students,  Northern  States 
Mason.  Connecticut 
Glassblower.  Massachusetts 
Blacksmith.  Connecticut 
Factory  operatives.  Massachusetts 
Brickmaker  at  hard  work.  Massachusetts 
Machinist  at  hard  work.  Massachusetts 


Man  with  little  muscular  work 
Man  at  moderate  work 
Man.  at  severe  work 


IG.  58.  —  DIETARIES  AND  DIETARY  STANDARDS. 

(From  Office  of  Experiment  Stations  Bulletin.) 

247 


248       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

equilibrium  ;  that  is,  the  income  and  outgo  of  nitrogen 
from  the  body  should  be  practically  equal. 

"  While  one  freely  admits  that  health  and  a  large  measure  of 
muscular  strength  may  be  maintained  upon  a  minimum  supply  of 
protein,  yet  I  think  that  a  dispassionate  survey  of  mankind  will  show 
that  races  which  adopt  such  a  diet  are  lacking  in  what,  for  want  of  a 
better  word,  one  can  only  describe  as  energy."  28 

On  the  other  hand,  excessive  and  unnecessarily  large 
amounts  of  protein  are  sometimes  consumed,  adding 
greatly  to  the  cost  of  the  ration  and  necessitating  ad- 
ditional labor  on  the  part  of  the  body  for  its  elimination. 

247.  Number  of  Meals  per  Day.  —  Some  persons  ad- 
vocate two  meals  per  day  rather  than  three,  but  dietary 
studies  show  that  the  best  results  are  secured  when 
the  food  is  divided  among  three  rather  than  two  meals, 
and  with  a  two-meal  system  the  tendency  is  to  con- 
sume a  larger  total  amount  of  food  than  when  three 
meals  are  eaten.  It  is  not  essential  that  the  food  be 
equally  divided  among  the  three  meals.  Any  one  of 
them  may  be  lighter  or  more  substantial  as  the  habits 
and  inclinations  of  the  individual  dictate.  If  it  is  found 
necessary  to  reduce  the  total  quantity  of  food  consumed, 
this  may  be  done  by  a  proportional  reduction  of  each 
of  the  meals,  or  of  any  one  of  them  instead  of  de- 
creasing the  number  of  meals  per  day.  The  occasional 
missing  of  a  meal  is  sometimes  beneficial,  in  cases  of 
digestion  disorders,  but  the  ordinary  requirements  of 
persons  in  normal  health  who  have  either  mental  or 


DIETARY    STUDIES  249 

physical  labor  to  perform  are  best  met  when  three  meals 
per  day  are  consumed,  as  this  insures  an  even  supply  of 
nutrients.  For  persons  of  sedentary  habits,  the  kind 
and  quantity  of  food  at  each  meal  must  be  regulated 
largely  by  the  individual  from  knowledge  based  on 
personal  experience. 

"  In  the  matter  of  diet  every  man  must,  in  the  last  resort,  be  a  law 
unto  himself;  but  he  should  draw  up  his  dietetic  code  intelligently 
and  apply  it  honestly,  giving  due  heed  to  the  warnings  which  nature 
is  sure  to  address  to  him  should  he  at  any  time  transgress."  28 

If  there  is  trouble  in  digesting  the  food,  it  is  well  to 
study  the  other  habits  of  life  along  with  the  food  question, 
for  it  may  be  the  difficulty  arises  from  some  other  cause, 
and.  would  be  remedied  by  more  exercise  and  fresh 
air,  avoiding  rush  immediately  after  meals,  more  thorough 
mastication,  or  less  worry.  It  is  a  serious  matter  to  shut 
off  the  supply  of  food  from  a  person  not  suffering  from 
some  disease  and  who  is  working ;  as  well  cut  off  the 
supply  of  fuel  from  a  furnace  and  then  expect  a  full 
amount  of  energy  and  heat.  But  unlike  the  furnace, 
when  the  human  body  is  deprived  of  needed  nutrients 
it  preys  upon  itself  and  uses  up  its  reserve  that  should 
be  drawn  upon  only  in  cases  of  illness  or  extreme 
nervous  strain.  Some  persons  live  in  such  a  way  as 
to  never  have  any  reserve  of  strength  and  energy  to 
call  upon  but  use  up  each  day  all  the  body  can  pro- 
duce and  so  become  physical  bankrupts  when  they 
should  be  in  their  prime.  Food  is  required  for  the 


250       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

production   of   nerve   energy  as  well   as   physical   en- 
ergy.78 

248.  Mixed  Dietary  Desirable.  —  Experiments  in  the 
feeding  of  farm  animals  show  that  the  best  results  come 
from  the  combination  of  a  number  of    foods    to  form 
a  mixed  ration,  rather  than  from  the  use  of  one  food 
alone,79  for  in  this  way  the  work  of  ^digestion  is  more 
evenly  distributed,  and  a  higher   degree  of    efficiency 
is  secured   from  the    foods    consumed.     The   same   is 
true  in  human  feeding ;  the    best  results  are   secured 
from  a  mixed  diet.     Ordinarily,  about  two  fifths  of  the 
nutrients  of  a  ration  are  derived  from  animal  and  three 
fifths  from  vegetable  sources. 

249.  Animal  and  Vegetable  Foods;  Economy  of  Pro- 
duction. —  Animal  foods  can  never  compete  in  cheapness 
of  the  nutrients  with  cereals  and  vegetables,  as  it  takes 
six  to  eight  pounds  or  more  of  a  cereal,  together  with 
forage  crops,  to  make  a  pound  of  meat.     Hence  the  re- 
turns in  food  value  are  very  much  larger  from  the  direct 
use  of  the  cereals  as  human  food,  than  from  the  feeding 
of  cereals  to  cattle  and  the  use  of  the  meat.     As  the 
population  of  a  country  increases,  and  foods  necessarily 
become  more  expensive,  cereals  are  destined  to  replace 
animal  foods  to  a  great  extent,  solely  as  a  matter  of 
economy. 

250.  Food  Habits.  —  Long-established  dietary  habits 
and    customs    are    not    easily    changed,   and  when  the 
body  becomes  accustomed  to  certain  foods,  substitution 


DIETARY    STUDIES  251 

of  others,  although  equally  valuable,  may  fail  to  give 
satisfactory  results.  For  example,  immigrants  from 
southern  Europe  demand  foods  with  which  they  are 
familiar,  as  macaroni,  olive  oil,  and  certain  kinds  of 
cheese,  foods  which  are  generally  imported  and  more 
expensive  than  the  staples  produced  in  this  country,80 
and  when  they  are  compelled  to  live  on  other  foods, 
even  though  they  have  as  many  nutrients,  they  complain 
of  being  underfed.  Previously  acquired  food  habits 
appear  to  affect  materially  the  process  of  digestion  and 
assimilation.  Sudden  and  pronounced  change  in  the 
feeding  of  farm  animals  is  attended  with  unsatisfactory 
results,  and  whenever  changes  are  made  in  the  food  of 
either  humans  or  animals  they  should  be  gradual  rather 
than  radical. 

251.  Underfed  Families.  — As  the  purchasing  of  food 
is  often  done  by  inexperienced  persons,  palatability 
rather  than  nutritive  value  is  made  the  basis  of  choice. 
Dietary  studies  show  that  because  of  lack  of  knowl- 
edge of  the  nutritive  value  of  foods,  whole  families  are 
often  underfed.  Particularly  is  this  true  where  the 
means  for  purchasing  foods  are  limited.  In  dietary 
studies  among  poor  families  in  New  York  City,81  the 
United  States  Department  of  Agriculture  notes :  "  It 
is  quite  evident  that  what  is  needed  among  these 
families  more  than  anything  else  is  instruction  in  the 
way  to  make  the  little  they  have  go  the  farthest." 
Some  classes  of  the  rich  too  are  equally  liable  to  be 


252        HUMAN    FOODS    AND  THEIR    NUTRITIVE    VALUE 

underfed,  as  they  are  more  prone  to  food  notions  and 
are  able  to  indulge  them.  Among  the  children  of  the 
rich  are  found  some  as  poorly  nourished  as  among  the 
poor. 

252.  Cheap  and  Expensive  Foods.  —  Among  the  more 
expensive  items  of  a  ration  are  meats,  butter,  and  canned 
fruits.      The   difference   in   composition   and   nutritive 
value    between    various  cuts   of   meat   is  small,  being 
largely  physical,  and  affecting  taste  and  flavor  rather 
than   nutritive  value.     Expensive   cuts  of  meat,  high- 
priced  breakfast  cereals,  tropical  fruits  and  foods  which 
impart  special  flavors,  add  little  in  the  way  of  nutritive 
value  to  the  ration,  but  greatly  enhance  the  cost  of  liv- 
ing.    Ordinarily  the  cheapest  foods  are  corn  meal,  wheat 
flour  and  bread,   milk,  beans,  cheese,  sugar,  and  pota- 
toes.7    The  amount  of  animal  and  vegetable  foods  to 
combine  with  these  to  form  a  balanced  ration  maybe 
governed   largely  by  personal   preference  or   cost,    as 
there  is  little  difference  in  nutritive  value.     The  selec- 
tion of  foods  on  the  basis  of  cost  and  nutritive  value  is 
discussed  in  Chapter  XVI. 

253.  Food    Notions.  —  Many  erroneous  ideas  exist  as 
to  the  nutritive  value  of  foods,  and  often  wholesome  and 
valuable   foods  are    discriminated  against   because   of 
prejudice.     Skim  milk  is  usually  regarded  as  containing 
little  if  any  nourishing  material,  when  in  reality  it  has  a 
high  protein  content,  and  can  be  added  to  other  foods 
to  increase  their  nutritive  value.    The  less  expensive  cuts 


DIETARY    STUDIES  253 

of  meat  contain  more  total  nutrients  than  many  of  the 
more  expensive  ones.  Beef  extracts  have  been  errone- 
ously said  to  contain  more  nutrients  than  beef,51  and 
mushrooms  to  be  equal  in  value  of  beefsteak ;  chemical 
analyses  fail  to  confirm  either  statement.  The  banana 
also  has  been  overestimated  as  to  food  value,  and  while 
it  contains  more  nutrients  than  many  fruits,  it  is  not  the 
equal  of  cereals,  as  has  been  claimed.82  Cocoa,  although 
a  valuable  beverage,  adds  but  little  in  the  way  of  nu- 
trients to  a  ration  unless  it  is  made  with  milk.  The 
value  of  a  food  should  be  based  upon  its  composition 
as  determined  by  chemical  analysis,  its  digestibility  as 
founded  upon  digestion  experiments,  and  its  palatability 
and  mechanical  structure.  Food  notions  have,  in  many 
instances,  been  the  cause  of  banishing  from  the  dietary 
wholesome  and  nutritious  foods,  of  greatly  increasing 
the  cost  of  living,  as  well  as  of  promulgating  incorrect 
ideas  in  regard  to  foods,  so  that  individuals  and  in  some 
cases  entire  families  have  suffered  from  improper  or  in- 
sufficient food. 

254.  Dietary  of  Two  Families  Compared.  —  A  dietary 
study  often  reveals  ways  in  which  it  is  possible  to  im- 
prove the  ration  in  kinds  and  amounts  of  food,  and 
sometimes  at  less  expense.  The  following  dietaries  of 
two  families  for  the  same  period  show  that  one  family 
expends  over  twice  as  much  in  the  purchase  of  foods  as 
the  other  family,  and  yet  the  one  whose  food  costs  the 
less  actually  secures  the  larger  amount  of  nutritive 


254       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

material  and  is  better  fed  than  the  family  where  more 
money  is  expended  for  food.13 


FOOD  CONSUMED,  ONE  WEEK. 


FAMILY  No.  i 


FAMILY  No.  2 


20  loaves  of  bread  .  .  .  $  1 .00 
10  to  12  Ib.  loin  steak,  or 

meat  of  similar  cost  .  .  2.00 
20  to  25  Ib.  rib  roast,  or 

similar  meat  ....  4.40 
4  Ib.  high-priced  cereal 

breakfast  food,  20  ct.  .  0.80 

Cake  and  pastry  purchased  3 .00 

8  Ib.  butter,  30  ct.  .  .  .  2.40 

Tea,  coffee,  spices,  etc.  .  0.75 

Mushrooms  .  .  .  .  .  0.75 

Celery i.oo 

Oranges 2.00 

Potatoes 0.25 

Miscellaneous  canned 

goods  ......  2.00 

Milk 0.50 

Miscellaneous  foods  .  .  2.00 

3  doz.  eggs 0.60 


$23.45 


15  Ib.  flour,    bread  home- 
made (skim  milk  used)  $0.45 

Yeast,    shortening    and 

skim  milk o.io 

10  Ib.  steak  (round,  Ham- 
burger, and  some  loin)  1.50 

10  Ib.  other   meats,   boil- 
ing pieces,  rump  roast, 

etc i.oo 

5  Ib.  cheese,  16  cents  .     .  0.80 

5  Ib.  oatmeal  (bulk)     .     .  0.15 

5  Ib.  beans 0.25 

Home-made     cake     and 

pastry i.oo 

6  Ib.  butter,  30  ct.   .     .     .  1.80 
3  Ib.  home-made  shorten- 
ing      0.25 

Tea,  coffee,  and  spices      .  0.40 

Apples 0.50 

Prunes 0.25 

Potatoes 0.25 

Milk i.oo 

Miscellaneous  foods     .     .  i.oo 

3  doz.  eggs 0.60 

$11  .30 


DIETARY    STUDIES  255 


Protein  .... 
FAMILY  No.  i  Fat 

Carbohydrates 
20  Ib.  bread  uz7zzzzzzzzz2ZX^*mmmmmm*^^mi^^mmm^^m^m^ammHm 


10  Ib.  loin  steak 

20  Ib.  rib  roast 
4  Ib.  cereals 
8  Ib.  butter 

25  Ib.  potatoes 

20  Ib.  milk 


FAMILY  No.  2 

15  Ib.  flour  twyy/w.//.// 

5  Ib.  skim  milk  em 

10  Ib.  round  steak  ysswsws^ 

10  Ib.  beef  »»„,„„* 

5  Ib.  cheese  WW/VW/M  : 

5  Ib.  oatmeal  ezzzzzx=mm 

6  Ib.  butter  I 
3  Ib.  shortening 

3  Ib.  prunes 
25  Ib.  apples 
25  Ib.  potatoes 
40  Ib.  milk 

5  Ib.  beans 


FIG.  59.  —  COST  AND  NUTRITIVE  VALUE  OF  RATIONS. 

In  comparing  the  foods  used  by  the  two  families,  it 
will  be  observed  that  family  No.  I  purchased  their  bread 
at  the  bakery  at  a  cost  of  $  i.oo,  while  the  bread  of 
family  No.  2  was  home-made,  skim  milk  being  used  in 


256      HUMAN    FOODS   AND    THEIR   NUTRITIVE   VALUE 

its  preparation,  the  flour,  milk,  yeast,  and  shortening  cost- 
ing about  55  cents.  Family  No.  I  consumed  10  pounds 
of  expensive  steaks,  family  No.  2  consumed  the  same 
number  of  pounds,  a  portion  being  cheaper  cuts.  In- 
stead of  the  20  pounds  of  roast  or  similar  beef  used  by 
family  No.  I,  only  one  half  as  much  and  cheaper  cuts 
as  boiling  pieces,  stew,  rump  roast,  etc.,  were  used  by 
family  No.  2  ;  5  pounds  of  beans  and  5  pounds  of  cheese 
taking  the  place  of  some  of  the  meat.  Family  No.  I 
consumed  4  pounds  of  high-priced  cereal  breakfast  foods, 
supposing  they  contained  a  larger  amount  of  nutrients 
than  were  actually  present.  In  place  of  the  4  pounds 
of  high-priced  cereal  breakfast  foods  of  family  No.  i, 
family  No.  2  used  5  pounds  of  oatmeal  purchased  in 
bulk.  Family  No.  I  bought  their  cake  and  pastry  for 
$3.00,  while  those  of  family  No.  2  were  home  made  and 
cost  $1.00.  Family  No.  2  used  2  pounds  less  butter  per 
week  because  of  the  preparation  and  use  of  home-made 
shortening  from  beef  suet  and  milk.  They  also  pur- 
chased a  smaller  amount  of  tea,  coffee,  and  spices  than 
family  No.  I.  Family  No.  2  consumed  a  larger  quantity 
of  less  expensive  fruits  and  vegetables  than  family  No.  i, 
who  ate  75  cents'  worth  of  mushrooms  with  the  idea  that 
they  contained  as  much  protein  as  meat,  but  analyses 
show  that  mushrooms  contain  no  more  nutrients  than 
potatoes  and  similar  vegetables.  In  place  of  the  celery 
and  oranges,  apples  and  prunes  were  used  by  family 
No.  2.  The  same  amount  of  potatoes  was  used  by  each. 
Fifty  cents  was  spent  for  milk  by  family  No.  i  and 


DIETARY    STUDIES 


257 


$1.00  by  family  No.  2.  The  total  amount  expended  for 
food  by  family  No.  I  was  $23.45,  while  family  No.  2 
purchased  a  greater  variety  of  foods  for  $11.30,  as  well 
as  foods  containing  more  nutrients.  The  approximate 
amounts  of  nutrients  in  the  foods  purchased  by  the  two 
families  are  given  in  the  following  table,  from  which  it 
will  be  observed  that  family  No.  2  obtained  a  much 
larger  amount  of  total  nutrients  and  was  better  fed  at 
considerably  less  expense  than  family  No.  i. 

NUTRIENTS  IN  FOODS  CONSUMED.  — FAMILY  No.  i 


PROTEIN 
LB. 

FAT 
LB. 

CARBOHYDRATES 
LB. 

20  Ib  bread             

I  98 

O.28 

1  1.  d.2 

10  Ib   loin  steak      

I   CO 

1.76 

20  Ib.  rib  roast       

L'jy 

2  68 

4  26 

4  Ib.  cereals     

o  42 

o  06 

2.7C 

8  Ib.  butter      

o  04 

680 

*'/  D 

25  Ib.  potatoes  

O  AC 

O  O"? 

r8* 

20  Ib.  milk    

O  7O 

o  80 

J'UJ 
I  OO 

7.86 

1.3-99 

19.00 

258      HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 
FAMILY  No.  2 


PROTEIN 
LB. 

FAT 
LB. 

CARBOHYDRATES 
LB. 

15  Ib.  flour    

I.8q 

O.I  2 

A 

II.  1C 

5  Ib.  skim  milk     

0.16 

O.OI 

0.26 

10  Ib.  round  steak        .... 
10  Ib.  beef    

1.81 

1.32 

1.26 

2.O2 

5  Ib.  cheese      

I  AO 

1  .7C 

5  Ib.  oatmeal    

0.78 

1  •/:> 
0.76 

3.J.O 

6  Ib.  butter      

O.O3 

c.io 

3  Ib.  shortenm0"    

2  CC 

3  Ib.  prunes     

O  O3 

**yj 

o  60 

25  Ib.  apples      

O  12 

2.  CO 

25  Ib.  potatoes        

O.AC 

O.O3 

^•y 

^.8^ 

40  Ib.  milk    .... 

I  A.A 

I  60 

I  QO 

5  Ib.  beans       .     .     .   •  . 

I   12 

i  .yu 

•5   QO 

10.55 

14.80 

26.64 

Difference  in  nutrients  in  favor 
of  family  No.  2,  consuming  the 
cheaper  combination  of  foods 

2.69 

0.81 

7.64 

255.  Food  in  its  Relation  to  Mental  and  Physical 
Vigor.  —  When  the  body  is  not  properly  supplied  with 
food,  the  best  results  in  the  form  of  productive  work 
cannot  be  secured.  There  is  a  close  relationship 
between  the  nature  of  the  food  consumed  and  mental 
activity,  also  ability  to  satisfactorily  perform  physical 
labor.  "The  productive  power  of  the  individual  as 
well  as  of  the  nation  depends  doubtless  upon  many 
factors  other  than  food,  such  as  race,  climate,  habit,  etc., 


DIETARY    STUDIES  259 

but  there  is  no  gainsaying  the  fact  that  diet  has  also  a 
profound  and  direct  influence  upon  it."83 

If  the  body  is  diseased,  it  cannot  make  the  right 
uses  of  the  food,  and  often  the  food  is  blamed  when 
the  trouble  is  due  primarily  to  other  causes.  The 
fact  that  a  diseased  digestive  tract  is  unable  to  utilize 
some  foods  is  no  valid  reason  why  these  foods  should 
be  discarded  in  the  dietary  of  persons  in  normal  health, 
particularly  when  the  food  is  in  no  way  responsible  for 
the  disease. 

Some  diseases  are  most  prevalent  in  the  case  of  a 
restricted  diet.  A  change  in  the  dietary  of  the  Japa- 
nese navy  greatly  improved  the  health  of  the  sailors. 

"  The  prevalence  of  kakke  or  beriberi  in  the  navy  turned  the  atten- 
tion of  many  medical  specialists  toward  the  problem  of  nutrition.  .  .  . 
It  was  generally  believed  that  there  was  some  very  close  connection 
between  the  disease  and  the  rice  diet.  .  .  .  One  outcome  of  these 
investigations  was  the  passage  of  the  food  supply  act  of  the  navy 
in  1884.  The  ration  provided  in  accordance  with  this  act  was 
sufficient  to  furnish  an  abundance  of  protein  and  energy.  .  .  .  Fol- 
lowing the  change  of  ration  in  1884,  the  prevalence  of  the  disease 
was  very  materially  diminished,  and  at  the  end  of  three  years 
cases  of  kakke  were  practically  unknown  among  the  marines.1"  83 

256.  Dietary  Studies  in  Public  Institutions.  —  Dietary 
studies  in  public  institutions,  as  prisons,  and  asylums 
for  the  insane,  show  that  it  is  possible  to  secure  greater 
variety  of  food  containing  a  larger  amount  of  nutrients, 
and  even  at  a  reduction  in  cost.84  In  such  institutions 
it  is  important  that  the  food  should  be  not  only  ample 


260       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

in  amount,  but  wholesome  and  nutritious,  as  many  of 
the  inmates  respond  both  physically  and  mentally  to 
an  improved  diet.  For  humanitarian  as  well  as  eco- 
nomic reasons  institutional  dietetics  should  more  gener- 
ally be  placed  under  the  supervision  of  skilled  dietists. 


CHAPTER   XVIII 
RATIONAL   FEEDING   OF   MAN 

257.  Object.  —  Rational  feeding  of  man  has   for   its 
object  the  regulation  of  the  food  supply  in  accord  with 
the  demands  of  the  body.     It  is  based  upon  the  same 
principles  as  the  rational  feeding  of  animals ;  in  each, 
the  best  results  in  the  way  of  health,   amount  of  labor 
performed,  and  economy  are  secured   when   the   body 
receives  nutrients  sufficient  for  the  production  of  heat 
and  energy  and  for  the  repair  of  worn-out  tissues.     Ra- 
tional  feeding  is  simply  regulation  of   the    food,  both 
as  to  kind  and  amount,  to  meet  the  needs  of  the  body.72 

258.  Standard  Rations.  —  In  human  feeding,   as   in 
animal  feeding,  it  is  not  possible  to  lay  down  hard  and 
fast  rules  as  to  the  quantity  of  nutrients  required  for 
a  standard  ration.85     As  stated  in  the  chapter  on  Die- 
tary Studies,  such  standards  have  been  proposed,  but 
they  are  to  be  considered  as  tentative  rather  than  abso- 
lute, for  the  amount  of  food  required  by  different  persons 
must   necessarily   vary  with    the    individuality.     While 
it  is   impossible  to    establish    absolute    standards,    any 
large  variation  from  the  provisional  standards  usually 

261 


262        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


results  in  lessened  ability  to  accomplish  work,  ill  health, 
or  increased  expense. 

259.  Amounts  of  Food  Consumed.  —  The  approximate 
amounts  of  some  food  articles  consumed  per  day  are 
as  follows : 


RANGE 

APPROXIMATE 
AMOUNT  IN  LBS. 

Bread     

6  to  14  oz. 

O.  SO 

Butter    

2  to  *5  OZ. 

0.  12 

Potatoes     

8  to  16  oz. 

.      O.7; 

Cheese  ....                    .... 

i  to    4  oz 

O  12 

Beans    *. 

i  to    4  oz. 

0.  12    * 

Milk       

8  to  32  oz. 

Su°"ar 

2  to    5  oz. 

O.2O 

Meats     

4  to  12  oz. 

0.2; 

Oatmeal      

I  to    4  oz. 

O.I2 

In  the  calculation  of  rations  it  is  desirable  that  the 
amount  of  any  food  article  should  not  exceed  that  des- 
ignated, unless  for  some  special  reason  it  has  been 
found  the  food  can  consistently  be  increased.  The 
amount  of  nutrients  given  in  dietary  standards  is  for 
one  day,  and  the  nutrients  may  be  divided  among  the 
three  meals  as  desired.  It  is  to  be  noted  that,  or- 
dinarily, the  foods  which  supply  carbohydrates  are 
flour,  corn  meal,  cereal  products,  potatoes,  beans,  sugar, 
and  milk;  those  which  supply  fat  are  milk,  butter, 
lard,  and  meats;  and  those  which  supply  protein  in 


RATIONAL    FEEDING    OF    MAN  263 

liberal  amounts  are  beans,  cheese,  meats,  oatmeal,  cereals, 
bread,  and  milk. 

260.  Average  Composition  of  Foods.  —  The  amounts 
of  nutrients  in  foods  are  determined  from  the  average 
composition  of  the  foods.  These  figures,  for  average 
composition  are  based  upon  analyses  of  a  large  number 
of  samples  of  food  materials.7  In  individual  cases  it 
will  be  found  that  foods  may  vary  from  the  standards 
given;  as  for  example,  milk  may  contain  from  2.5  to  5 
per  cent  of  fat,  while  the  protein  and  fat  of  meats  vary 
appreciably  from  the  figures  given  for  average  compo- 
sition. With  the  cereals  and  vegetable  foods,  variations 
from  the  standards  are  small.  In  the  table,  the  com- 
position of  the  food  as  purchased  represents  all  of  the 
nutrients  in  the  food,  including  those  in  the  refuse, 
trimmings,  or  waste,  while  the  figures  for  the  edible  por- 
tion represent  the  nutrients  in  the  food  after  deducting 
what  is  lost  as  refuse.  In  making  calculations,  the 
student  should  use  the  figures  given  for  the  foods  as 
purchased,  unless  the  weights  are  of  the  edible  portion 
only.  The  figures  in  the  table  are  on  the  basis  of  per- 
centage amounts,  or  nutrients  in  100  pounds  of  food. 
By  moving  the  decimal  point  two  places  to  the  left,  the 
figures  will  represent  the  nutrients  in  one  pound,  and 
if  this  is  multiplied  by  the  number  of  pounds  or  fraction 
of  a  pound  used,  the  quantity  of  nutrients  is  secured. 
For  example,  suppose  bread  contains  9.5  per  cent  of 
protein  and  56  per  cent  of  carbohydrates,  I  pound 


264      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

would  contain  0.095  pound  of  protein,  0.56  pound  of 
carbohydrates ;  and  0.5  of  a  pound  would  contain 
approximately  0.05  pound  of  protein  and  0.28  pound 
of  carbohydrates.  In  calculating  rations,  it  is  not 
necessary  to  carry  the  figures  to  the  third  decimal 
place. 


FIG.  60.  — FOOD  ARTICLES  FOR  A  HUMAN  RATION. 

261.  Example  of  a  Ration.  —  Suppose  it  is  desired  to 
calculate  a  ration  for  a  man  at  light  muscular  work. 
Firsf,  note  the  requirements  in  the  way  of  nutrients  in 
the  table  "  Dietary  Standards,"  Section  246.  Such  a 
ration  should  supply  approximately  0.22  pound  each  of 
protein  and  fat,  and  0.77  pound  of  carbohydrates,  and 
should  yield  2800  calories.  A  trial  ration  is  made  by 
combining  the  following : 


RATIONAL    FEEDING    OF    MAN 


265 


Pound 

Bread          .         

0.50 

Butter         

O.I2 

Potatoes     
Milk   

0.75 
I.OO 

Sugar          .                 .        
Beef  

0.12 

O  2C 

ir.^3 

O  ^O 

Oatmeal      

Ep-prc 

0.12 
O.2C 

v"*3 

The  quantities  of  nutrients  in  these  food  materials  are 
approximately  as  follows : 

RATION  FOR  MAN  AT  MODERATE  WORK 


LB. 

PROTEIN 
LB. 

FAT 
LB. 

C.H. 
LB. 

CALORIES 

Bread              

O   CO 

O  OC 

O  OI 

O  2Q 

6c? 

Butter        

W'3W 

O.I2 

O.  IO 

U3J 

A32 

Potato  

O.7C 

O  OI 

O   12 

4J  * 
•2AA 

Milk      

I.OO 

O  OA. 

O  O4. 

O  OS 

^44 

727 

Suj?ar    . 

O.I2 

0.  12 

J^J 
IQ2 

Beef  (round)       .... 
Ham      

0.25 
O  2O 

0.05 

o  03 

O.O3 

O  O7 

iy^ 

218 

77T 

Oatmeal     

O   12 

O  O2 

O  OI 

o  08 

JJ1 

•227 

EffCTc 

O.2C 

O  O7 

O.O7 

•**J 

l6A 

J-^&&a 
Squash  

O.2O 

O  OI 

2i? 

-:) 

0.23 

0.29 

0.67 

2805 

It  is  to  be  noted  that  this  ration  contains  approxi- 
mately the  amount  of  protein  called  for  in  the  standard 


266      HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

ration,  while  the  fat  is  slightly  more  and  the  carbohy- 
drates are  less.  The  food  value  of  the  ration  is  prac- 
tically that  called  for  in  the  standard.  This  ration  is 
sufficiently  near  the  standard  to  supply  the  nutrient 
requirements  of  a  man  at  light  muscular  work.  To 
supply  palatability,  some  fruit  and  vegetables  should 
be  added  to  the  ration.  These  will  contribute  but  little 
to  the  nutrient  content,  but  are  necessary  in  order  to 
secure  health  and  the  best  returns  from  the  other  foods, 
and  as  previously  stated,  they  are  not  to  be  estimated 
entirely  upon  the  basis  of  nutrient  content.  A  number 
of  food  articles  could  be  substituted  in  this  ration,  if 
desired,  either  in  the  interests  of  economy,  palatability, 
or  personal  preference. 

262.  Requisites  of  a  Balanced  Ration.  —  Reasonable 
combinations  of  foods  should  be  made  to  form  balanced 
rations.2  A  number  of  foods  slow  of  digestion,  or  which 
require  a  large  amount  of  intestinal  work,  should 
not  be  combined;  neither  should  foods  which  are 
easily  digested  and  which  leave  but  little  indigestible 
residue.  After  a  ration  has  been  calculated  and  found 
to  contain  the  requisite  amount  of  nutrients,  it  should  be 
critically  examined  to  see  whether  or  not  it  fulfills  the 
following  requirements : 

1 .  Economy  and  adaptability  to  the  work  required. 

2.  Necessary  bulk  or  volume. 

3.  Desired  physiological  influence  of  the  foods  upon  the  digestive 

tract,  whether  constipating  or  laxative  in  character. 

4.  Ease  of  digestion. 


RATIONAL    FEEDING    OF    MAN  267 

5.  Effect  upon  health.  It  is  recognized  that  there  are  foods 
wholesome  and  nutritious,  that  cannot  be  used  by  some  per- 
sons, while  with  others  the  same  foods  can  be  consumed 
with  impunity. 

As  explained  in  the  chapter  on  Dietary  Studies,  the 
nutrients  should  be  supplied  from  a  number  of  foods 
rather  than  from  a  few,  because  it  is  believed  the  various 
nutrients,  particularly  the  proteins,  are  not  absolutely 
identical  from  all  sources,  or  equal  in  nutritive  value. 

EXAMPLES 

1.  Calculate  a  ration  for  a  man  with  little  physical  exercise. 

2.  Calculate  a  ration  for  a  man  at  hard  muscular  labor,  and  give 

the  approximate  cost  of  the  ration. 

3.  Calculate  the  amounts  of  food  and  the  nutrient  requirements 

for  a  family  of  seven  for  10  days ;  five  of  the  family  to  con- 
sume 0.8  as  much  as  an  adult.  Calculate  the  cost  of  the 
food ;  then  calculate  on  the  same  basis  the  probable  cost  of 
food  for  one  year,  adding  20  per  cent  for  fluctuation  in 
market  price  and  additional  foods  not  included  in  the  list. 

4.  Weigh  out  the  food  articles  used  in  problem  No.  2,  and  appor- 

tion them  among  three  meals. 


CHAPTER    XIX 
WATER 

263.  Importance.  —  Water  is  one  of  the  most  essential 
food  materials.     It  enters  into  the  composition  of  the 
body,  and  without  it  the  nutrients  of  foods  would   be 
unavailable,   and  life    could    not  be  sustained.     Water 
unites  chemically  with  various  elements    to  form  plant 
tissue  and  supplies  hydrogen  and  oxygen  for  the  produc- 
tion of  'organic  compounds  within  the  leaves  of  plants. 
In    the    animal    economy    it    is    not    definitely    known 
whether  or  not  water  furnishes  any  of  the  elements  of 
which  the  tissues  are  composed,  as  the  food  contains 
liberal  amounts  of  hydrogen  and  oxygen  ;  it  is  necessary 
mainly  as  the  vehicle  for  distributing  nutrients  in  sus- 
pension and  solution,  and  as  a  medium  in  which  chemical, 
physical,  and  physiological   changes    essential    to   life 
processes  take  place.     From  a  sanitary  point  of  view, 
the  condition  of  the  water  supply  is  of  great  importance, 
as  impure  water  seriously  affects  the  health  of  the  con- 
sumer.87 

264.  Impurities  in  Water.  —  Waters  are  impure  be- 
cause of:  (i)  excessive  amounts  of  alkaline  salts  and 
other  mineral   compounds  ;    (2)    decaying  animal  and 

268 


WATER 


269 


vegetable  matters  which  act  chemically  as  poisons  and 
irritants,  and  which  may  serve  as  food  for  the  develop- 
ment of  objectionable  bacterial  bodies;  and  (3)  injurious 


FIG.  61.  —  DIRT^  AND  IMPURITIES  IN  A  SURFACE  WELL  WATER. 

bacteria.  The  most  common  forms  of  impurities  are 
excess  of  organic  matter  and  bacterial  contamination. 
The  sanitary  condition  of  water  is  greatly  influenced  by 
the  character  of  the  soil  through  which  it  flows  and  the 
extent  to  which  it  has  been  polluted  by  surface  drain- 
age.88 


270       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

265.  Mineral  Impurities.  -*-  The  mineral  impurities  of 
water  are  mainly  soluble  alkaline  and  similar  compounds 
dissolved  by  the  water  in  passing  through  various  layers 
of  soil  and  rock.  When  water  contains  a  large  amount 
of  sodium  chloride,  sodium  sulphate  or  carbonate,  or 
other  alkaline  salts,  it  is  termed  an  "  alkali  water." 
Where  water  passes  through  soil  that  has  been  largely 
formed  from  the  decay  of  rocks  containing  alkaline 
minerals,  the  water  dissolves  some  of  these  minerals  and 
becomes  alkaline.  The  kind  of  alkali  determines  the 
character  of  the  water ;  in  some  cases  it  is  sodium  car- 
bonate, which  is  particularly  objectionable.  The  con- 
tinued use  of  strong  alkali  water  causes  digestion  dis- 
orders, because  of  the  irritating  action  upon  the  digestive 
tract.  -Hard  waters  are  due  to  the  presence  of  lime 
compounds.  In  regions  where  limestone  predominates, 
the  carbon  dioxid  in  water  acts  as  a  solvent,  producing 
hard  waters.  Waters  that  are  hard  on  account  of  the 
presence  of  calcium  carbonate  give  a  deposit  when 
boiled,  due  to  liberation  of  the  carbon  dioxid  which  is 
the  material  that  renders  the  lime  soluble.  *  Calcium 
sulphate,  or  gypsum,  on  the  other  hand,  imparts  per- 
manent hardness.  There  is  no  deposit  when  such 
waters  are  boiled.  A  large  number  of  minerals  are 
found  in  various  waters,  often  sufficient  in  amount  to 
impart  physiological  properties.  Water  that  is  highly 
charged  with  mineral  matter  is  difficult  to  improve 
sufficiently  for  household  purposes.  About  the  only 
way  is  by  distillation.89 


WATER  271 

266.  Organic  Impurities.  —  Water  that  flows  over  the 
surface  of  the  ground  comes  in  contact  with  animal  and 
vegetable  material  in  various  stages  of  decay,  and  as  a 
result  some  is  dissolved  and  some  is  mechanically  carried 
along  by  the  water.     After  becoming  soluble,  the  organic 
matter  undergoes  further  chemical  changes,  as  oxidation 
and  nitrification  caused  by  bacteria.       If   the   organic 
matter  contain  a  large  amount  of  nitrogenous  material, 
particularly    of  proteid    origin,    a   series    of    chemical 
changes  induced  by  bacterial  action  takes  place,  resulting 
in  the  production  of  nitrites.       The  nitrifying  organisms 
first  produce  nitrous  acid  products  (nitrites),  and  in  the 
further  development  of  the  nitrifying  process  these  are 
changed  to  nitrates.     The  ammonia  formed  as  the  result 
of  the  decomposition  of  nitrogenous  organic  matter  readily 
undergoes  nitrification  changes.       Nitrates  and  nitrites 
alone  are   not  injurious  in  water,  but  they  are  usually 
associated   with    objectionable    bacteria    and  .generally 
indicate  previous  contamination.90 

267.  Interpretation   of    a   Water   Analysis.  — "  Total 
solid  matter"  represents  all  the  mineral,  vegetable,  and 
animal  matter  which  a  water  contains.     It  is  the  residue 
obtained  by  evaporating  the  water  to  dryness  at  a  tem- 
perature of  212°  F.     Average  drinking  water  contains 
from  20  to  90  grains  per  gallon  of  solid  matter.     "  Free 
ammonia"  is  that  formed  as  a  result  of  the  decomposi- 
tion of  animal  or  vegetable  matter  containing  nitrogen. 
Water  of  high  purity  usually  contains  less    than   0.07 


272       HUMAN    FOODS    AND    THEIR    NUTRITIVE   VALUE 

parts  per  million  of  free  ammonia.  "  Albuminoid  am- 
monia "  is  derived  from  the  partially  decomposed  ani- 
mal or  vegetable  material  in  water.  The  greater  the 
amount  of  nitrogenous  organic  impurities,  the  higher 
the  albuminoid  ammonia.  A  good  drinking  water  ought 
not  to  contain  more  than  o.io  part  per  million  of  albu- 
minoid ammonia.  An  abnormal  quantity  of  chlorine 
indicates  surface  drainage  or  sewage  contamination,  or 
an  excess  of  alkaline  matter,  as  common  salt.  Nitrites 
should  not  be  present,  as  they  are  generally  associated 
with  matter  not  completely  oxidized.  Nitrites  are  usu- 
ally considered  more  objectionable  than  nitrates;  both 
are  innocuous  unless  associated  with  disease-producing 
nitroorganisms. 

268.  Natural  Purification  of  Water.  —  River   waters 
are  sometimes  dark  colored  because  of  large  amounts  of 
dissolved  organic  matter,  but  in  contact  with  the   sun 
and  air  they  gradually  undergo  natural  purification  and 
the  organic  matter  is  oxidized.     However,  absolute  reli- 
ance cannot  be  placed  upon  natural  purification  of   a 
bad  water,  as  the  objectionable  organisms  often   have 
great  resistive  power.    There  is  no  perfectly  pure  water 
except  that  prepared  in  the  chemical  laboratory  by  dis- 
tillation.    All  natural  waters  come  in  contact  with  the 
soil  and  air,  and  necessarily  contain  impurities  propor- 
tional to  the  extent  of  their  contamination. 

269.  Water  in  Relation  to  Health.  — There  are  many 
diseases,  of  which  typhoid  fever  is  a  type,  that  are  dis- 


WATER  273 

tinctly  water-born.  The  typhoid  bacilli,  present  in  count- 
less numbers  in  the  feces  of  persons  suffering  or  con- 
valescent from  typhoid  fever,  find  their  way  into  streams, 
lakes,  and  wells.91  They  retain  their  vitality,  and  when 
they  enter  the  digestive  tract  of  an  individual,  rapidly 
increase  in  numbers.  Numerous  disastrous  outbreaks 
of  typhoid  fever  have  been  traced  to  contamination  of 
water.  Coupled  with  the  sanitary  improvement  of  a 
city's  water  supply,  there  is  diminution  of  typhoid  fever 
cases,  and  a  noticeable  lowering  of  the  death  rate. 
Many  cities  and  villages  are  dependent  for  their  water 
upon  rivers  and  lakes  into  which  surface  drainage  finds 
its  way,  with  all  contaminating  substances.  Mechanical 
sedimentation  and  filtration  greatly  improve  waters  of 
this  class,  but  do  not  necessarily  render  them  entirely 
pure.  Compounds  of  iron  and  aluminium  are  sometimes 
added  in  small  amounts,  under  chemical  supervision, 
to  such  waters  to  precipitate  the  organic  impurities. 
Spring  waters  are  not  entirely  above  suspicion,  as  often- 
times the  soil  through  which  they  flow  is  highly  polluted. 
All  water  of  doubtful  purity  should  be  boiled,  and  there 
are  but  few  natural  waters  of  undoubted  purity.  There 
is  no  such  thing  as  absolutely  pure  water  in  a  state  of 
nature.  The  mountain  streams  perhaps  approach  near- 
est to  it  where  there  are  no  humans  to  pollute  the  banks  ; 
but  then  there  are  always  the  beasts  and  birds,  and  they, 
too,  are  subject  to  disease.  There  are  very  few  waters 
that  at  some  time  of  the  year  and  under  some  conditions 
are  not  contaminated  with  disease-producing  organisms. 


274        HUMAN    FOODS    AND    THEIR   NUTRITIVE   VALUE 

No  matter  how  carefully  guarded  are  the  banks  of  lakes 
furnishing  the  water  supply  of  cities,  more  or  less  ob- 
jectionable matter  will  get  in.  In  seasons  of  heavy  rains, 
large  amounts  of  surface  water  enter  the  lakes,  carrying 
along  the  filth  gathered  from  many  acres  of  land  drained 
by  the  streams  entering  the  lakes.  Some  of  the  most 
serious  outbreaks  of  typhoid  fever  have  come  from 
temporary  contamination  of  ordinarily  fairly  good  drink- 
ing water.  In  general,  too  little  attention  is  given  to  the 
purity  of  drinking  water.  It  is  just  as  important  that 
water  should  be  boiled  as  that  food  should  be  cooked. 
One  of  the  objects  of  cooking  is  to  destroy  the  injurious 
bacteria,  and  they  are  frequently  more  numerous  in  the 
drinking  water  than  in  the  food. 

The  argument  is  sometimes  advanced  that  the  min- 
eral matter  present  in  water  is  needed  for  the  construc- 
tion of  the  bone  and  other  tissues  of  the  body,  and  that 
distilled  water  fails  to  supply  the  necessary  mineral 
matter.  This  is  an  erroneous  assumption,  as  the  min- 
eral matter  in  the  food  is  more  than  sufficient  for  this 
purpose.  When  water  is  highly  charged  with  mineral 
salts,  additional  work  for  their  elimination  is  called  for 
on  the  part  of  the  organs  of  excretion,  particularly  the 
kidneys;  and  furthermore,  water  nearly  saturated  with 
minerals  cannot  exert  its  full  solvent  action. 

In  discussing  the  immediate  benefits  resulting  from 
improvement  of  water,  Fuertes  says : 92 

"Immediately  after  the  change  to  the  <  four  mile  intake1  at  Chi- 
cago in  1893,  there  was  a  great  reduction  in  typhoid.  Lawrence, 


WATER  275 

Mass.,  showed  a  great  improvement  with  the  setting  of  the  filters  in 
operation  in  September,  1893  ;  fully  half  of  the  deaths  in  1894  were 
among  persons  known  to  have  used  the  unfiltered  canal  water. 
The  conclusion  is  warranted  that  for  the  efficient  control  of  the 
death  rate  from  typhoid  fever  it  is  necessary  to  have  efficient  sewer- 
age and  drainage,  proper  methods  of  living,  and  pure  water.  The 
reason  why  our  large  cities,  which  are  all  provided  with  sewerage, 
have  such  high  death  rates  is  therefore  without  doubt  their  continu- 
ance of  the  filthy  practice  of  supplying  drinking  water  which  carries 
in  solution  and  suspension  the  washings  from  farms,  from  the 
streets,  from  privies,  frorkl  pigpens,  and  the  sewage  of  cities.  .  .  . 
And  also  we  should  recoVnize  the  importance  of  flies  and  other 
winged  insects  and  birds  wjiich  feed  on  offal  as  carriers  of  bacteria 
of  specific  diseases  from  points  of  infection  to  the  watersheds,  and 
the  consequent  washing  of  newly  infected  matter  into  our  drinking 
water  by  rains." 

There  is  a  very  close  relationship  between  the  sur- 
face water  and  that  of  shallow  wells.  A  shallow  well 
is  simply  a  reservoir  for  surface  water  accumulations. 
It  is  stated  that,  when  an  improved  system  of  drainage 
was  introduced  into  a  part  of  London,  many  of  the 
shallow  wells  became  dry,  indicating  the  source  from 
which  they  received  their  supply.  Direct  subterranean 
connection  between  cesspools  and  wells  is  often  traced 
in  the  following  way:  A  small  amount  of  lithium, 
which  gives  a  distinct  flame  reaction,  and  a  minute  trace 
of  which  can  be  detected  with  the  spectroscope,  is 
placed  in  the  cesspool,  and  after  a  short  time  a  lithium 
reaction  is  secured  from  the  well  water. 

Rain  water  is  relied  upon  in  some  localities  for  drink- 
ing purposes.  That  collected  in  cities  and  in  the  vicin- 


276       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

ity  of  barns  and  dwellings  contains  appreciable  amounts 
of  organic  impurities.  The  brown  color  is  due  to  the 
impurities,  ammonium  carbonate  being  one  of  these. 
There  are  also  traces  of  nitrates  and  nitrites  obtained 
from  the  air.  When  used  for  drinking,  rain  water 
should  be  boiled. 

270.  Improvement  of  Waters.  —  Waters  are  improved 
by:  (i)   boiling,  which  destroys  the  disease-producing 
organisms ;  (2)  filtration,  which  removes  the  materials 
mechanically  suspended  in  the  water ;  and  (3)  distilla- 
tion, which  eliminates  the  impurities  in  suspension  and 
solution,  as  well  as  destroys  all  germ  life. 

271.  Boiling  Water.  —  In  order  to  destroy  the  bac- 
teria that  may  be  in  drinking  water,  it  is  not  sufficient 
to  heat  the  water  or  merely  let  it  come  to  a  boil.     It 
has  been  found  that  if  water  is  only  partially  sterilized 
and  then  cooled  in  the  open  air,  the  bacteria  develop 
more  rapidly  than  if  the  water  had  not  been  heated  at 
all.      It   should    boil   vigorously   five   to   ten   minutes ; 
cholera  and  typhoid  bacteria  succumb  in  five  minutes 
or  less.     Care  should  be  taken  in  cooling  that  the  water 
is  not  exposed  to  dust  particles  from  the  air  nor  placed 
in  open  vessels  in  a  dirty  refrigerator.     It  should  be 
kept  in  perfectly  clean,  tight-stoppered  bottles.     These 
bottles   should   be   frequently   scalded.     Great  reliance 
may  be  placed  upon  this  method  of  water  purification 
when  properly  carried  out. 


WATER 


277 


272.  Filtration.  —  Among  the  most  efficient  forms  of 
water  filters  are  the  Berkefeld  and  Pasteur.  The  Pas- 
teur filter  is  made  of  unglazed 
porcelain,  and  the  Berkefeld 
of  fine  infusorial  earth  (finely 
divided  SiO2).  Both  are  por- 
ous and  allow  a  moderately 
rapid  flow  of  water.  The 
flow  from  the  Berkefeld  fil- 
ter is  more  rapid  than  from 
the  Pasteur.  The  mechani- 
cal impurities  of  the  water 
are  deposited  upon  the  filter- 
ing surface,  due  to  the  attrac- 
tion which  the  material  has 
for  particles  in  suspension. 
These  particles  usually  are 
the  sources  of  contamination 
and  carry  bacteria.  When 
first  used,  filters  are  satisfac- 
tory, but  unless  carefully 
looked  after  they  soon  lose 
their  ability  to  remove  germs  from  the  water  and  may 
increase  the  impurity  by  accumulation.  Small  faucet 
filters  are  made  of  porous  stone,  asbestos,  charcoal,  etc. 
Many  of  them  are  of  no  value  whatever  or  are  even  worse 
than  valueless.  Filters  should  be  frequently  cleansed  in 
boiling  water  or  in  steam  under  pressure.  Unless  this 
is  done,  the  filters  may  become  incubators  for  bacteria. 


FIG.  62.-— PASTEUR  WATER 
FILTERS. 


278       HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

273.  Distillation.  —  When  an  unquestionably  pure 
water  supply  is  desired,  distillation  should  be  resorted 
to.  There  are  many  forms  of  stills  for  domestic  use 
which  are  easily  manipulated  and  produce  distilled 
water  economically.93  The  mineral  matter  of  water  is 


FIG.  63.— WATER  STILL. 

in  no  way  essential  for  any  functional   purpose,  and 
hence  its  removal  through  distillation  is  not  detrimental. 

274.  Chemical  Purification.  —  Purification  of  water  by 
the  use  of  chemicals  should  not  be  attempted  in  the 
household  or  by  inexperienced  persons.  When  done 
under  supervision  of  a  chemist  or  bacteriologist,  it  may 
be  of  great  value  to  a  community.  Turneaure  and 


WATER  279 

Russell,94   in    discussing   the   purification   of  water  by 
addition  of  chemicals,  state: 

"  There  are  a  considerable  number  of  chemical  substances  that  may 
be  added  to  water  in  order  to  purify  it  by  carrying  down  the  sus- 
pended matter  as  well  as  bacteria,  by  sedimentation.  Such  a  pro- 
cess of  purification  is  to  be  seen  in  the  addition  of  alum,  sulphate  of 
iron,  and  calcium  hydrate  to  water.  Methods  of  this  character  are 
directly  dependent  upon  the  flocculating  action  of  the  chemical 
added,  and  the  removal  of  the  bacteria  is  accomplished  by  subsid- 


275.  Ice,  —  The  purity  of  the  ice  supply  is  also  of 
much  importance.     While  freezing  reduces  the  number 
of  organisms  and  lessens  their  vitality,  it  does  not  make 
an  impure  water  absolutely  wholesome.     The  way,  too, 
in  which  ice  is  often  handled  and  stored  subjects  it  to 
contamination,    and    foods  which  are  placed  in  direct 
contact  with  it  mechanically  absorb  the  impurities  which 
it  contains.     For  cooling  water,   ice  should  be  placed 
around   rather  than   in   it.     Diseases   have   frequently 
been  traced  to  impure  ice.     The  only  absolutely  pure 
ice  is  that  made  from  distilled  water. 

276.  Mineral  Waters.  — When  water  is  charged  with 
carbonic  acid  gas  under  pressure,  carbonated  water  re- 
sults, and  when  minerals,  as  salts  of  sodium,  potassium, 
or  lithium,  are  added,  artificial  mineral  waters  are  pro- 
duced.     Natural    mineral   waters   are   placed    on   the 
market  to   some  extent,   but  most  mineral  waters  are 
artificial   products    and   they   are    sometimes    prepared 
from  water  of  low  sanitary  character.     Mineral  waters 


280       HUMAN    FOODS   AND   THEIR   NUTRITIVE    VALUE 

should  not  be  used  extensively  except  under  medical 
direction,  as  many  have  pronounced  medicinal  proper- 
ties. Some  of  the  constituents  are  bicarbonates  of  so- 
dium, potassium,  and  lithium ;  sulphates  of  magnesium 
(Epsom  salts)  and  calcium;  and  chloride  of  sodium* 
The  sweetened  mineral  waters,  as  lemonade,  orangeade, 
ginger  ale,  and  beer,  contain  sugar  and  organic  acids,  as 
citric  and  tartaric,  and  are  flavored  with  natural  or  arti- 
ficial products.  Most  of  them  are  prepared  without 
either  fruit  or  ginger.  Natural  mineral  waters  used 
under  the  direction  of  a  physician  are  often  beneficial 
in  cases  of  chronic  digestion  disorders  or  other  diseases. 

277.  Materials  for  Softening  Water.  —  The  materials 
most  commonly  used  for  softening  water  are  sodium 
carbonate  (washing  soda),  borax,  ammonia,  ammonium 
carbonate,  potash,  and  soda  lye.  Waters  that  are  very 
hard  with  limestone  should  have  a  small  amount  of 
washing  soda  added  to  them.  Two  ounces  for  a  large 
tub  of  water  is  the  most  that  should  be  used,  and  it 
should  first  be  dissolved  in  a  little  water.  If  too  much 
soda  is  used,  it  is  injurious,  as  only  a  certain  amount  can 
be  utilized  for  softening  the  water,  and  the  excess  simply 
injures  the  hands  and  fabric.  When  hard  limewater  is 
boiled  and  a  very  little  soda  lye  added,  a  precipitate  of 
carbonate  of  lime  is  formed,  and  then  if  the  water  is 
strained,  it  is  greatly  improved  for  washing  purposes. 
Borax  is  valuable  for  making  some  hard  waters  soft. 
It  is  not  as  strong  in  its  action  as  is  sodium  carbonate. 


WATER  28l 

For  the  hardest  water  ^  pound  of  borax  to  a  large  tub- 
ful  may  be  used ;  most  waters,  however,  do  not  need  so 
much.  Ammonia  is  one  of  the  most  useful  reagents 
for  softening  water.  It  is  better  than  washing  soda 
and  borax,  because  the  ammonia  is  volatile  and  does 
not  leave  any  residue  to  act  on  the  clothes,  thus  causing 
injury.  For  bathing  purposes,  the  water  should  be 
softened  with  ammonia,  in  preference  to  any  other 
material.  Ammonia  should  not  be  poured  directly  into 
hot  water ;  it  should  be  added  to  the  water  while  cold, 
or  to  a  small  quantity  of  cold  water,  and  then  to  the 
warm  water,  as  this  prevents  the  ammonia  from  vapor- 
izing too  readily.  Ammonia  produces  the  same  effect 
as  potash  or  soda  lye,  without  leaving  a  residue  in  the 
garments  washed.  It  is  especially  valuable  in  washing 
woolen  goods  or  materials  liable  to  shrink.  Waters 
which  are  hard  with  alum  salts  are  greatly  benefited  by 
the  addition  of  ammonia.  A  little  in  such  a  water  will 
cause  a  precipitate  to  form,  and  when  the  water  is 
strained  it  is  in  good  condition  for  cleaning  purposes. 
Ammonium  carbonate  is  used  to  some  extent  as  a  soft- 
ening and  cleaning  agent,  and  is  valuable,  as  there  is  no 
injurious  effect  upon  clothing,  because  it  readily  volatil- 
izes. Caustic  potash  and  caustic  soda  are  sometimes 
employed  for  softening  water,  but  they  are  very  active 
and  are  not  adapted  to  washing  colored  or  delicate 
fabrics.  They  may  be  used  for  very  heavy  and  coarse 
articles  that  are  greasy,  —  not  more  than  a  gram  in  a 
gallon  of  water.  Bleaching  powder  is  not  generally  a 


282       HUMAN    FOODS    AND   THEIR    NUTRITIVE   VALUE 

safe  material  for  cleansing  purposes,  as  it  weakens  the 
texture  of  clothing.  After  a  contagious  disease,  articles 
may  be  soaked  in  water  containing  a  little  bleaching 
powder  and  a  few  drops  of  carbolic  acid,  followed  by 
thorough  rinsing  and  bleaching  in  the  sun.  But  as  a 
rule  formaline  is  preferable  for  disinfecting  clothing. 
It  can  be  used  at  the  rate  of  about  one  pound  to  100 
gallons  of  water.  Bleaching  powder,  caustic  potash 
or  soda,  and  strong  soap  are  not  suitable  for  cleaning 
woodwork,  because  of  the  action  of  the  alkali  on  paint 
and  wood ;  they  roughen  the  surface  and  discolor  the 
paint  Waters  vary  so  in  composition,  that  a  material 
suitable  for  softening  one  may  not  prove  to  be  the  best 
for  softening  another.  The  special  kind  must  be  de- 
termined largely  by  trial,  and  it  should  be  the  aim  to 
use  as  little  as  possible.  When  carbolic  acid,  formaline, 
bleaching  powder,  and  caustic  soda  are  used,  the  hands 

should  be  protected  and  the  clothes 

should  be  well  rinsed. 

278.    Economic  Value   of   a  Pure 
Water   Supply.  —  From  a  financial 
point  of  view,  the  money  spent  in 
securing  pure  water  is  one  of  the 
FIG.  64.— TYPHOID      best  investments  a  community  can 
make.      Statisticians     estimate     the 
death  of  an  adult  results  in  a  loss  to  the  state  of  from 
$1000  to  $5000;  and  to  the  losses  sustained  by  death 
must  be  added  those  incurred  by  sickness  and  by  less- 


WATER  283 

ened  quality  and  quantity  of  work  through  impaired 
vitality,  —  all  caused  by  using  poor  drinking  water. 
Wherever  plants  have  been  installed  for  improving  the 
sanitary  condition  of  the  water  supply,  the  death  rate 
has  been  lowered  and  the  returns  to  the  community 
have  been  far  greater  than  the  cost  of  the  plant.  Im- 
pure water  is  the  most  expensive  food  that  can  be 
consumed. 


CHAPTER   XX 

FOOD  AS  AFFECTED  BY  HOUSEHOLD  SANITATION 
AND  STORAGE 


279.  Injurious  Compounds   in   Foods.  —  An  ordinary 
chemical  analysis  of  a  food  determines  only  the  nutri- 
ents, as   protein,  carbohydrates,  and  fats  ;    and   unless 
there  is  reason  to  believe  the  food  contains  injurious 
substances  no  special  tests  for  these  are  made.     There 
are  a  number  of  poisonous  compounds  that  foods  may 
contain,  and    many    of   them    can    but   imperfectly  be 
determined    by   chemical  analysis.     Numerous  organic 
compounds  are  produced  in  foods  as  the  result  of  the 
workings  of  microorganisms  ;  some  of  these  are  poison- 
ous, while    others   impart  only   special   characteristics, 
as  taste  and  odor.     The  poisonous  bacteria  finding  their 
way  into  food  produce  organic  compounds  of  a  toxic 
character  ;  and  hence  it  is  that  the  sanitary  condition 
of  a  food,  as  influenced  by  preparation  and  storage,  is 
often   of    more    vital    importance    than    the    nutrient 
content. 95 

280.  Sources  of  Contamination  of  Food.  —  As  a  rule, 
too  little  attention  is  given  to  the  sanitary  handling  and 
preparation  of  foods.    They  are  often  exposed  to  impure 

284 


FOOD   AS   AFFECTED   BY   SANITATION   AND   STORAGE       285 

air  and  to  the  dust  and  filth  from  unclean  streets  and 
surroundings,  and  as  a  result  they  become  inoculated 
with  bacteria,  which  are  often  the  disease-producing 
kind.  Gelatine  plates  exposed  by  bacteriologists  under 
the  same  conditions  as  foods  develop  large  numbers  of 


FIG.  65.— TUBERCULOSIS  BACILLI.     (After  CONN.) 
Often  present  in  dust  particles  and  contaminated  foods. 

injurious  microorganisms.  In  order  to  avoid  contami- 
nation in  the  handling  of  food,  there  must  be:  (i)  pro- 
tection from  impure  air  and  dust ;  (2)  storage  in  clean, 
sanitary,  and  ventilated  storerooms  and  warehouses; 
(3)  storage  of  perishable  foods  at  a  low  temperature  so 
as  to  reta'fd  fermentation  changes ;  and  (4)  workmen  free 
from  contagious  diseases  in  all  occupations  pertaining 


286       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

to  the  preparation  of  foods.  Ordinarily,  foods  should 
not  be  stored  in  the  paper  wrappers  in  which  they 
are  purchased,  as  unclean  paper  is  often  a  source  of 
contamination. 

281.  Sanitary  Inspection  of  Food.  —  During  recent 
years  some  state  and  city  boards  of  health  have  in- 
troduced sanitary  inspection  of  foods,  with  a  view 
of  preventing  contamination  during  manufacture  arid 
transportation,  and  this  has  done  much  to  improve 
the  quality  and  wholesomeness.  Putrid  meats,  fish,  and 
vegetables  are  not  allowed  to  be  sold,  and  foods  are 
required  to  be  handled  and  stored  in  a  sanitary  way. 
Next  to  a  pure  water  supply,  there  is  no  factor  that  so 
greatly  influences  for  good  the  health  of  a  community 
as  the  sanitary  condition  of  the  food.  While  the  cook- 
ing of  foods  destroys  many  organisms,  it  often  fails  to 
render  innocuous  the  poisons  which  they  produce,  and 
furthermore  the  unsound  foods  when  cooked  are  not  en- 
tirely wholesome,  and  they  have  poor  keeping  qualities. 

Often  meats,  vegetables,  and  other  foods  eaten  un- 
cooked, as  well  as  the  numerous  cooked  foods,  are 
exposed  in  dirty  market  places,  and  accumulate  large 
amounts  of  filth,  and  are  inoculated  with  disease  germs 
by  flies.  Protection  of  food  from  flies  is  a  matter  of 
vital  importance,  as  they  are  carriers  of  many  diseases. 
In  the  case  of  typhoid  fever,  next  to  impure  drinking 
water  flies  are  credited  with  being  the  greatest  dis- 
tributors of  the  disease  germs.96 


FOOD   AS   AFFECTED    BY   SANITATION   AND   STORAGE       287 

282.  Infection  from  Impure  Air.  —  The  dust  particles 
of  the  air  contain  decayed  animal  and  vegetable  matter 
in  which  bacteria  are  present ;  these  find  their  way  into 
the  food  when  it  is  not  carefully  protected,  into  the 
water  supply,  and  also  into  the  lungs  and  other  organs 


FIG.  66.  —  DIPHTHERIA  BACILLI.    (After  CONN.) 
Often  present  in  dust  particles  and  in  food  unprotected  from  dust. 

of  the  body.  When  foods  are  protected  from  the  me- 
chanical impurities  which  gain  access  through  the  air, 
and  fermentation  is  delayed  by  storage  at  a  low  tem- 
perature, digestion  disorders  are  greatly  lessened.  From 
a  sanitary  point  of  view,  the  air  of  food  storerooms  and 
of  living  rooms  should  be  of  equally  high  purity.  When 
foods  are  kept  in  unventilated  living  rooms,  they  become 


288       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

contaminated  with  the  impurities  thrown  off  from  the 
lungs  in  respiration,  which  include  not  only  carbon  di- 
oxid,  but  the  more  objectionable  toxic  organic  materials. 
Vegetable  foods  need  to  be  stored  in  well-ventilated 
places,  as  the  plant  cells  are  still  alive  and  carrying  on 
life  functions,  as  the  giving  off  of  carbon  dioxid,  which 
is  .akin  to  animal  respiration  ;  in  fact,  it  is  plant-cell 
respiration.  Provision  should  be  made  for  the  removal 
of  the  carbon  dioxid  and  other  products,  as  they  con- 
taminate the  air.  When  vegetable  tissue  ceases  to  pro- 
duce carbon  dioxid,  death  and  decay  set  in,  accompanied 
by  fermentation  changes. 

283.  Storage  of  Food  in  Cellars.  —  Cellars  are  often 
in  a  very  unsanitary  condition,  damp,  poorly  lighted,  un- 
ventilated,  and  the  air  filled  with  floating  particles  from 
decaying  vegetables.  The  walls  and  shelves  absorb  the 
dust  and  germs  from  the  foul  air  and  are  bacterially  con- 
taminated, and  whenever  a  sound  food  is  stored  in  such 
a  cellar,  it  readily  becomes  inoculated  with  bacteria. 
There  is  a  much  closer  relationship  existing  between  the 
atmosphere  of  the  cellar  and  that  of  the  house  than  is 
generally  realized.  An  unclean  cellar  means  contami- 
nated air  throughout  the  house.  When  careful  attention 
is  given  to  the  sanitary  condition  of  the  cellar,  many  of 
the  more  common  diseases  are  greatly  reduced.  Cases 
of  rheumatism  have  often  been  traced  to  a  damp  cellar. 
In  some  localities  where  the  cellars  are  unusually  un- 
sanitary, there  is  in  the  season  of  spring  rains,  when 


FOOD   AS    AFFECTED   BY    SANITATION    AND    STORAGE       289 

they  are  especially  damp  and  contain  the  maximum  of 
decayed  vegetation,  a  prevalence  of  what  might  be  called 
"cellaritis."  The  symp- 
toms differ  and  the 
trouble  is  variously  at- 
tributed, but  the  real 
cause  is  the  same,  al- 
though overlooked,  for, 
unfortunately,  doctors 
do  not  visit  the  cellar. 
Cellars  should  be 
frequently  cleaned  and 
disinfected,  using  for 
the  purpose  some  of 
the  well-known  disin- 
fectants, as  formaline, 
bleaching  powder,  or  a 
dilute  solution  of  car- 
bolic acid.  It  has  been 
found  in  large  cities, 
when  the  spread  of 
such  diseases  as  yellow 
fever  was  imminent, 
that  a  general  and  thorough  cleaning  up  of  streets  and 
cellars  with  the  improved  sanitary  conditions  resulting 
greatly  lowered  the  usual  death  rate. 


FIG.  67.  —  DUNG  FUNGUS. 

(After  BUTTERS.) 

Often  present  on  surface  of  unclean 

vegetables. 


284.    Sunlight,  Pure  Water,  and   Pure  Air   as  Disin- 
fectants. —  The  most  effectual  and  valuable  disinfectants 


2QO       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

are  sunlight,  pure  water,  and  pure  air.  Many  kinds  of 
microorganisms,  particularly  those  that  are  disease-pro- 
ducing, are  destroyed  when  exposed  for  a  time  to  sun- 
light. The  chemical  action  of  the  sun's  rays  is  destructive 
to  the  organic  material  which  makes  up  the  composition 
of  many  of  these  organisms,  while  higher  forms  of  or- 
ganic life  are  stirred  into  activity  by  it.  The  disinfecting 
power  of  sunlight  should  be  made  use  of  to  the  fullest 
extent,  not  only  in  the  house,  but  plenty  of  sunlight 
should  also  be  planned  for  in  constructing  barns  and 
other  buildings  where  milk-  and  meat-producing  animals 
are  kept.  Pure  water  is  also  a  disinfectant,  but  when 
water  becomes  polluted  it  loses  this  power.  Many  dis- 
ease-producing organisms  are  rendered  inactive  when 
placed  in  pure  water.  Water  contains  more  dissolved 
oxygen  than  air,  and  apparently  a  portion  of  the  oxygen 
in  water  is  in  a  more  active  condition  than  that  in  air. 
Pure  air,  too,  is  a  disinfectant ;  the  ozone  and  hydrogen 
peroxide  and  oxides  of  nitrogen,  which  are  present  in 
traces,  exert  a  beneficial  influence  in  oxidizing  organic 
matter.  Fresh  air  and  sunlight,  acting  jointly,  are  na- 
ture's most  effectual  disinfectants.  Sunshine,  fresh  air, 
and  pure  water  are  a  health-producing  trinity.  In  dis- 
cussing the  importance  of  pure  air,  water,  and  sunlight, 
Ellen  H.  Richards97  says  : 

"  The  country  dweller  surrounds  his  house  with  evergreens  or  shade 
trees,  the  city  dweller  is  surrounded  with  high  brick  walls.  Blinds, 
shades,  or  thick  draperies  shut  out  still  more,  and  prevent  the  bene- 
ficial sunlight  from  acting  its  r61e  of  germ  prevention  and  germ 


FOOD    AS    AFFECTED    BY    SANITATION    AND    STORAGE 


destruction.  Bright-colored  carpets  and  pale-faced  children  are  the 
opposite  results  which  follow.  Sunlight,  pure  air,  and  pure  water  are 
our  common  birthright  which  we  often  bargain  away  for  so-called 
comforts." 

And  Dr.  Woods  Hutchinson  says  of  sunlight : 

"  It  is  a  splendid  and  matchless  servant  in  the  promoting  of 
healthfulness  of  the  house,  for  which  no  substitute  has  yet  been  dis- 
covered. It  is  the  foe  alike  of  bacilli  and  the  blues  ;  the  best  tonic 
ever  yet  invented  for  the  liver  and  for  the  scalp,  and  for  everything 
between,  the  only  real  complexion  restorer,  and  the  deadliest  foe  of 
dirt  and  disease." 

285.  Utensils  for  Storage  of  Food.  —  In  order  that 
dishes  and  household  utensils  may  be  kept  in  the 
best  sanitary  condition,  they  should  be  free  from  seams, 
cracks,  and  crevices  where 
dust  and  dirt  particles  can 
find  lodgment.  From  the 
seams  of  a  milk  pail  that 
has  not  been  well  washed, 
decaying  milk  solids  can 
be  removed  with  the  aid 
of  a  pin  or  a  toothpick. 
This  material  acts  as  a 
"  starter  "  or  culture  when 
pure,  fresh  milk  is  placed 
in  the  pail,  contaminating 
it  and  causing  it  to  become 
sour.  Not  only  is  this  true  of  milk,  but  also  of  other 
foods.  Wooden  utensils  are  not  satisfactory  for  the 


FIG.    68.  — DIRT   AND   MANURE  EM- 
BEDDED IN  SURFACE  OF  CELERY. 


2Q2       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

handling,  storage,  or  preparation  of  foods,  as  it  is  diffi- 
cult to  keep  wood  in  a  sanitary  condition.  Uncleanliness 
of  dishes  in  which  foods  are  placed  is  too  often  caused 
by  the  use  of  foul  dishcloths  and  failure  to  thoroughly 
wash  and  rinse  the  dishes.  It  is  always  well  to  rinse 
dishes  with  scalding  water^  as  colds  and  skin  diseases 
may  be  communicated  from  the  edges  of  drinking  glasses, 
and  from  forks  and  spoons,  and,  unless  the  dish  towels 
are  kept  scrupulously  clean,  it  is  more  sanitary  to  drain 
the  dishes  than  to  wipe  them. 

286.  Contamination  from  Unclean  Dishcloths.  — When 
the  dishcloth  is  foul,  the  fat  absorbed  by  the  fibers  be- 
comes rancid,  the  proteids  undergo  putrefaction  changes 
with  formation  of  ill-smelling  gases  containing  nitrogen, 
the  carbohydrates  ferment  and  are  particularly  attractive 
to  flies,  and  all  the  various  disease  germs  collected  on  the 
surface  of  the  dishcloth  are,  along  with  the  rancid  fat 
and  other  putrifying  materials,  distributed  over  the  sur- 
face of  the  dishes  with  which  the  cloth  comes  in  contact. 

287.  Refrigeration.  —  At  a   low  temperature  the  in- 
soluble or  unorganized  ferments  become  inactive,  but 
the  chemical  ferments  or  enzymes  are  still  capable  of 
carrying  on  fermentation.     Thus  it  is  that  a  food,  when 
placed  in  a  refrigerator  or  in  cold  storage,  continues  to 
undergo  chemical  change.     An  example  of  such  enzymic 
action  is  the  curing  of  beef  and  cheese  in  cold  storage. 
A  small  amount  of  ventilation  is  required  when  foods  are 
refrigerated,  just  sufficient  to  keep  up  a  slight  circulation 


FOOD   AS    AFFECTED    BY    SANITATION   AND    STORAGE        293 

of  air.  It  seems  not  to  be  generally  understood  that  all 
fermentation  changes  do  not  cease  when  food  is  placed 
in  refrigerators,  and  this  often  leads  to  neglect  in  their 
care.  Cleanliness  is  equally  as  essential,  or  more  so,  in 
the  refrigeration  of  food  as  in  its  handling  in  other  ways. 


FIG.  69.  —  CONTAMINATION  OF  WELL  WATER  FROM  SURFACE  DRAINAGE. 
(After  Farmers'  Bulletin,  U.  S.  Dept.  Agr.) 

Too  often  the  refrigerator  is  neglected,  milk  and  other 
food  is  spilt,  filling  the  cracks,  and  slow  decomposition 
sets  in.  A  well-cared-for  refrigerator  is  an  important 
factor  in  the  preservation  of  food,  but  when  it  is  neg- 
lected, it  becomes  a  source  of  contamination.  Unclean 
vegetables  and  food  receptacles,  impure  ice  and  foul  air, 
are  the  most  common  forms  of  contamination.  The 


2Q4       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

chemical  changes  which  foods  undergo  during  refriger- 
ation are  such  as  result  in  softening  of  the  tissues. 

288.  Soil.  —  The  soil  about  dwellings  and  places  where 
foods  are  stored  frequently  becomes  polluted  with  de- 
caying animal  and  vegetable  matter,  and  in  such  soils 
disease-producing     organisms     readily    find    lodgment. 
Poorly  drained  soils  containing  an  excess  of  vegetable 
matter  furnish  a  medium  in  which  the  tapeworm  and  the 
germs  of  typhoid  fever,  lockjaw,  and  various  diseases 
affecting  the  digestive  tract,  may  propagate.     The  wind 
carries    the   dust    particles    from    these     contaminated 
places    into  unprotected    food,  where  they   cause  fer- 
mentation changes  and   the   disease    germs    multiply. 
In  considering  the  sanitary     condition    of     a    locality, 
the  character  of  the  soil  is  an  important  factor.      When- 
ever there  is  reason  to  suspect  that  a  soil  is  unsanitary, 
it  should  be  disinfected  with  lime  or  formaldehyde.  Soils 
about  dwellings  need  care  and  frequent  disinfecting  to 
keep  them  in  a  sanitary  condition,  equally  as  much  as 
do  the  rooms  in  the  dwellings."     In  the    growing  of 
garden  vegetables,   frequently  large  quantities  of  ferti- 
lizers of  unsanitary  character  are  used,  and  vegetables 
often  retain  mechanically  on  their  surfaces  particles  of 
these.     To  this  dirt  clinging  to  the  vegetables  have  been 
traced  diseases,  as  typhoid  fever  and  various  digestion 
disorders. 

289.  Disposal  of  Kitchen  Refuse.  —  Refuse,  as  vege- 
table parings,  bones,  and  meat  scraps,  unless  they  are 


FOOD    AS    AFFECTED    BY    SANITATION    AND    STORAGE        295 

used  for  food  for  animals  or  collected  as  garbage,  should 
preferably  be  burned ;  then  there  is  no  danger  of  their 
furnishing  propagating  media  for  disease  germs.  Gar- 
bage cans  should  be  kept  clean,  and  well  covered  to 
protect  the  contents  from  flies.  Where  the  refuse  cannot 
be  burned,  it  should  be  composted.  For  this,  a  well- 
drained  place  should  be  selected,  and  the  refuse  should 
be  kept  covered  with  earth  to  keep  off  the  flies  and 
absorb  the  odors  that  arise  from  the  fermenting  material, 
and  to  prevent  its  being  carried  away  by  the  wind. 
Lime  should  be  sprinkled  about  the  compost  heap,  and 
from  time  to  time  it  should  be  drawn  away  and  the  place 
covered  with  clean  earth.  It  is  very  unsanitary  to 
throw  all  of  the  kitchen  refuse  in  the  same  place  year 
after  year  without  resorting  to  any  means  for  keeping 
the  soil  in  a  sanitary  condition.  Although  composting 
refuse  is  not  as  sanitary  as  burning,  it  is  far  more  sani- 
tary than  neglecting  to  care  for  it  at  all,  as  is  too  fre- 
quently the  case. 

Ground  polluted  with  kitchen  refuse  containing  large 
amounts  of  fatty  material  and  soap  becomes  diseased,  so 
that  the  natural  fermentation  changes  fail  to  take  place, 
and  the  soil  becomes  "  sewage  sick  "  and  gets  in  such  a 
condition  that  vegetation  will  not  grow.  Failure  to 
properly  dispose  of  kitchen  refuse  is  frequently  the  cause 
of  the  spread  of  germ  diseases,  through  the  dust  and 
flies  that  are  attracted  by  the  material  and  carry  the 
germs  from  the  refuse  pile  to  food. 

Where  there  is  no  drainage  system,  disposal  of  the 


296       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

liquid  refuse  is  a  serious  problem.  Drain  basins  and 
cesspools  are  often  resorted  to,  and  these  may  become 
additional  sources  of  contamination.  As  stated  in  the 
chapter  on  well  water,  direct  communication  is  frequently 
established  between  such  places  and  shallow  wells. 


PLUMBING  OF  SINK. 


I,  I,  house  side  of  trap,  filled  with  water;  2,  vent  pipe ;  3,  drain  pipe  connect- 
ing with  sewer. 

Where  the  only  place  for  the  disposal  of  waste  water  is 
the  surface  of  the  ground,  it  should  be  thrown  some  dis- 
tance from  the  house  and  where  it  will  drain  from  and 
not  toward  the  well.  The  land  should  be  well  drained 
and  open  to  the  sunlight.  Coarse  sand  and  lime  should 
be  sprinkled  over  it  frequently,  and  occasionally  the  soil 
should  be  removed  and  replaced  with  fresh.  Sunlight, 
aeration,  and  disinfection  of  the  soil  and  good  drainage 


FOOD   AS    AFFECTED   BY   SANITATION   AND    STORAGE       297 

are  necessary,  in  order  to  keep  in  a  sanitary  condition 
the  place  where  the  dish  water  is  thrown. 

Poor  plumbing  is  often  the  cause  of  contaminated 
food.  The  gases  which  escape  from  unclean  traps  may 
carry  with  them  solid  particles  of  organic  matter  in 
various  stages  of  decay.  The  "house  side"  of  traps 
always  ventilates  into  the  rooms,  and  hence  it  is  impor- 
tant that  they  be  kept  scrupulously  clean.  Where  the 
drip  pipe  from  the  refrigerator  drains  directly  into  the 
sewerage  system,  there  is  always  danger.  Special  atten- 
tion should  be  given  to  the  care  of  plumbing  near  places 
where  foods  are  stored.  Frequently  there  are  leaky 
joints  due  to  settling  of  the  dwellings  or  to  extreme 
changes  in  temperature,  and  the  plumbing  should  be 
occasionally  inspected  by  one  familiar  with  the  sub- 
ject.100 

290.  General  Considerations.  —  In  order  to  keep  food 
in  the  most  wholesome  condition,  special  care  should  be 
taken  that  all  of  its  surroundings  are  sanitary.  The  air, 
the  dishes  in  which  the  food  is  placed,  the  refrigerator, 
cellar  or  closet  where  stored,  and  the  other  food  with 
which  it  comes  in  contact,  all  influence  the  wholesome- 
ness  or  cause  contamination.  A  food  may  contain 
sufficient  nutrients  to  give  it  high  value,  and  yet,  on 
account  of  products  formed  during  fermentation,  be 
poisonous.  Foods  are  particularly  susceptible  to  putre- 
faction changes,  and  chemicals  and  preservatives  added 
as  preventives,  with  a  view  of  retarding  these  changes, 


298       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

are  objectionable,  besides  failing  to  prevent  all  fermenta- 
tion from  taking  place.       Intelligent  thought  should  be 


FIG.  71.  — A  PETRT  DISH,  SHOWING  COLONIES  OF  BACTERIA  PRODUCED 

BY  ALLOWING  A  HOUSE   FLY  TO  CRAWL  OVER   SURFACE. 
(From  Minnesota  Experiment  Station  Bulletin  No.  93.) 

exercised  in  the  care  of  food,  for  the  health  of  the  con- 
sumer is  largely  dependent  upon  the  purity  and  whole- 
someness  of  the  food  supply. 


CHAPTER   XXI 
LABORATORY  PRACTICE 

Object  of  Laboratory  Practice,  Laboratory  Note-book,  and  Sugges- 
tions for  Laboratory  Practice.  —  The  aim  of  the  laboratory  practice 
is  to  give  the  students  an  idea  of  the  composition,  uses,  and  values 
of  food  materials,  and  the  part  which  chemistry  takes  in  sanitation 
and  household  affairs  ;  also  to  enable  them  by  simple  tests  to  detect 
some  of  the  more  common  adulterants  in  foods. 

Before  performing  an  experiment,  the  student  is  advised  to  review 
those  topics  presented  in  the  text  which  have  a  bearing  upon  the 
experiment,  so  that  a  clear  conception  may  be  gained  of  the  relation- 
ship between  the  laboratory  work  and  that  of  the  class  room.  The 
student  should  endeavor  to  cultivate  the  power  of  observation  and  to 
grasp  the  principle  involved  in  the  work,  rather  than  do  it  in  a  merely 
mechanical  and  perfunctory  way.  Neatness  is  one  of  the  essentials  for 
success  in  laboratory  practice,  and  too  much  emphasis  cannot  be  laid 
upon  this  requisite  to  good  work.  The  student  should  learn  to  use  his 
time  in  the  laboratory  profitably  and  economically.*  He  should 
obtain  a  clear  idea  of  what  he  is  to  do,  and  then  do  it  to  the  best 
of  his  ability.  If  the  experiment  is  not  a  success,  repeat  it.  While 
the  work  is  in  progress  it  should  be  given  undivided  attention.  Care 
should  be  exercised  to  prevent  anything  getting  into  the  sinks  that 
will  clog  the  plumbing ;  soil,  matches,  broken  glass,  and  paper  should 
be  deposited  in  the  waste  jars. 

A  careful  record  of  the  experiments  should  be  kept  by  each  student 
in  a  suitable  note-book.  It  is  suggested  that  those  students  desiring 
more  time  in  writing  out  the  experiments  than  the  laboratory  period 
affords,  take  notes  as  they  make  the  various  tests,  and  then  amplify 
and  rearrange  them  in  the  evening  study  time.  The  final  writing  up 
of  the  notes  should,  however,  be  done  before  the  next  laboratory 

299 


300       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

period.  Careful  attention  should  be  given  to  the  spelling,  language, 
and  punctuation,  and  the  note-book  should  represent  the  student's 
individual  work.  He  who  attempts  to  cheat  by  copying  the  results 


FIG.  72.  — APPARATUS  USED  IN  LABORATORY  WORK. 
See  page  301  for  names. 

of  others,  only  cheats  himself.     In  recording  the  results  of  an  experi- 
ment, the  student  should  state  briefly  and  clearly  the  following : 

1.  Number  and  title  of  experiment. 

2.  How  the  experiment  is  performed. 

3.  What  was  observed. 

4.  What  the  experiment  proves. 


LABORATORY   PRACTICE 


3OI 


FIG.  73.  —  BALANCE  AND  WEIGHTS. 


LIST  OF  APPARATUS  USED 

1  Crucible  Tongs 

2  Evaporating  Dishes 
i  Casserole 

6  Beakers 
12  Test  Tubes 
i  Wooden  Stand 
i  Test  Tube  Stand 

1  Sand  Bath 

2  Funnels 
i  Tripod 

i  Stoddart  Test  Tube  Clamp 


IN  EXPERIMENTS 
i  Test  Tube  Brush 

1  Burner  and  Tubing 

2  Stirring  Rods 
6  Watch  Glasses 

2  Erlenmeyer  Flasks 
i  Package  Filter  Paper 
i  Box  Matches 

1  Wire  Gauze 

2  Burettes 

i  Porcelain  Crucible 
i  Aluminum  Dish 


302       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 


FIG.  74. 


Directions  for  Weighing.  —  Place  the  dish  or  material  to  be 
weighed  in  the  left-hand  pan  of  the  balance.  With  the  forceps  lay 
a  weight  from  the  weight  box  on  the  right-hand  pan. 
Do  not  touch  the  weights  with  the  hands.  If  the 
weight  selected  is  too  heavy,  replace  it  with  a  lighter 
weight.  Add  weights  until  the  pans  are  counter- 
poised ;  this  will  be  indicated  by  the  needle  swinging 
nearly  as  many  divisions  on  one  side  of  the  scale 
as  on  the  other.  The  brass  weights  are  the  gram 
weights.  The  other  weights  are  fractions  of  a  gm.  The 
500,  200,  100  mg.  (milligram)  weights  are  recorded  as 
0.5,  0.2,  and  o.i  gm.  The  50,  20,  and  10  mg.  weights 
as  0.05,  0.02,  and  o.oi  gm.  If  the  10,  and  2  gm.,  and 
the  200,  the  100,  and  the  50  mg.  weights  are  used,  the 
resulting  weight  is  12.35  gms-  No  moist  substances 
should  ever  come  in  contact  with  the  scale  pans.  The  weights  and 
forceps  should  always  be  replaced  in  the  weight  box.  Too  much 
care  and  neatness  cannot  be 
exercised  in  weighing. 

Directions  for  Measuring.  — 
Reagents  are  measured  in  gradu- 
ated cylinders  (see  Fig.  74). 
When  the  directions  call  for  the 
addition  of  5  or  10  cc.  of  a  re- 
agent, unless  so  directed  it  is  not 
absolutely  necessary  to  measure 
the  reagent  in  a  measuring  cyl- 
inder. A  large  test  tube  holds 
about  30  cc.  of  water.  Measure 
out  5  cc.  of  water  and  transfer 
it  to  a  large  test  tube.  Note  FIG.  75.  — POURING  REAGENT  FROM 
its  volume.  Add  approximately 

5  cc.  of  water  directly  to  the  test  tube.  Measure  it.  Repeat  this 
operation  until  you  can  judge  with  a  fair  degree  of  accuracy  the 
part  of  a  test  tube  filled  by  5  cc.  In  the  experiments  where  a 


LABORATORY    PRACTICE 


303 


burette  is  used  for  measuring  reagents,  the  burette  is  first  filled  with 
the  reagent  by  means  of  a  funnel.  The  tip  of  the  burette  is  allowed 
to  fill  before  the  readings  are  made,  which  are  from  the  lowest  point 
or  meniscus.  When  reagents  are  removed  from  bottles,  the  stopper 


FIG.  76.  —  MICROSCOPE  AND  ACCESSORIES. 
i,  eye-piece  or  ocular ;  2,  objective;  3,  stage;  4,  cover  glass;  5,  slide;  6,  mirror. 

should  be  held  between  the  first  and  second  fingers  of  the  right 
hand  (see  Fig.  75).  Hold  the  test  tube  or  receptacle  that  is  to 
receive  the  reagent  in  the  left  hand.  Pour  the  liquid  slowly  until  the 
desired  amount  is  secured.  Before  inserting  the  stopper,  touch  it  to 
the  neck  of  the  bottle  to  catch  the  few  drops  on  the  edge,  thus  pre- 
venting their  streaking  down  the  sides  of  the  bottle  on  to  the  shelf. 


304       HUMAN    FOODS   AND   THEIR    NUTRITIVE    VALUE 

Replace  the  bottle  in  its  proper  place.     Every  precaution  should  be 
taken  to  prevent  contamination  of  reagents. 

Use  of  the  Microscope.  —  Special  directions  in  the  use  of  the  micro- 
scope will  be  given  by  the  instructor.  The  object  or  material  to  be 
examined  is  placed  on  a  microscopical  slide.  Care  should  be  exer- 
cised to  secure  a  representative  sample,  and  to  properly  distribute 
the  substance  on  the  slide.  If  a  pulverized  material  is  to  be  exam- 
ined, use  but  little  and  spread  it  in  as  thin  a  layer  as  possible.  If  a 
liquid,  one  or  two  drops  placed  on  the  slide  will  suffice.  The  mate- 
rial on  the  slide  is  covered  with  a  cover  glass,  before  it  is  placed  on 
the  stage  pf  the  microscope.  In  focusing,  do  not  allow  the  object 
glass  of  the  microscope  to  come  in  contact  with  the  cover  glass. 
Focus  upward,  not  downward.  Special  care  should  be  exercised  in 
focusing  and  in  handling  the  eye-piece  and  objective.  A  camel's-hair 
brush,  clean  dry  chamois  skin,  or  clean  silk  only  should  be  used  in 
polishing  the  lenses.  Always  put  the  microscope  back  in  its  case 
after  using. 


Experiment  No.  i 
Water  in  Flour 

Carefully  weigh  a  porcelain  or  aluminum  dish.  (Porcelain  must  be 
used  if  the  ash  is  to  be  determined  on  the  same  sample.)  Place  in  it 
about  2  gm.  of  flour;  record  the  weight;  then  place  the  dish  in  the 
water  oven  for  at  least  6  hours.  After  drying,  weigh  again,  and  from 
the  loss  of  weight  calculate  the  per  cent  of  water  in  the  flour. 
(Weight  of  flour  and  dish  before  drying  minus  weight  of  flour  and 
dish  after  drying  equals  weight  of  water  lost.  Weight  of  water 
divided  by  weight  of  flour  taken,  multiplied  by  100,  equals  the  per  cent 
of  water  in  the  flour.) 

How  does  the  amount  of  water  you  obtained  compare  with  the 
amount  given  in  the  tables  of  analysis  ? 


LABORATORY    PRACTICE  305 

Experiment  No.  2 
Water  in  Butter 

Carefully  weigh  a  clean,  dry  aluminum  dish,  place  in  it  about  2 
gms.  of  butter,  and  weigh  again.  Record  the  weights.  Place  the 
dish  containing  butter  in  the  water  oven  for  5  or  6  hours  and  then 
weigh.  The  loss  in  weight  represents  the  water  in  the  butter. 
Calculate  Nthe  per  cent  of  water.  Care  must  be  taken  to  get  a 
representative  sample  of  the  butter  to  be  tested ;  preferably  small 
amounts  should  be  taken  with  the  butter  trier  from  various  parts  of 
the  package. 

Experiment  No.  3 
Ash  in  Flour 

Place  the  porcelain  dish  containing  flour  from  the  preceding  ex- 
periment in  a  muffle  furnace  and  let  it  remain  until  the  organic 
matter  is  completely  volatilized.  Cool,  weigh,  and  determine  the  per 
cent  of  ash.  The  flour  should  be  burned  at  the  lowest  temperature 
necessary  for  complete  combustion. 

Experiment  No.  4 
Nitric  Acid  Test  for  Nitrogenous  Organic  Matter 

To  3  cc.  of  egg  albumin  in  a  test  tube  add  2  cc.  of  HNO3  (cone.) 
and  heat.  When  cool  add  NH4OH.  The  nitric  acid  chemically 
reacts  upon  the  albumin,  forming  yellow  xanthoprotein.  What 
change  occurs  in  the  appearance  of  the  egg  albumin  when  the 
HNO3  is  added?  Is  this  a  physical  or  chemical  change?  What 
is  the  name  of  the  compound  formed?  What  change  occurs  on 
adding  NH4OH? 

Experiment  No.  5 
Acidity  of  Lemons 

With  a  pipette  measure  into  a  small  beaker  2  cc.  of  lemon  juice. 
Add  25  cc.  of  water  and  a  few  drops  of  phenolphthalein  indicator. 


, 


306       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

From  the  burette  run  in  N/io  KOH  solution  until  a  faint  pink  tinge 
remains  permanently.  Note  the  number  of  cubic  centimeters  of 
KOH  solution  required  to  neutralize  the  citric  acid  in  the  lemon 
juice.  Calculate  the  per  cent  of  citric  acid. 

(i  cc.  of  N/io  KOH  solution  equals  0.00642  gm.  citric  acid, 
i  cc.  of  H2O  weighs  I  gm.  Because  of  sugar  and  other  matter  in 
solution  i  cc.  of  lemon  juice  weighs  approximately  1.03  gm.) 

i.    What  is  the  characteristic  acid  of  lemons?     2.    What  is  the 
salt  formed  when  the  lemon  juice  is  neutralized  by  the  KOH  solu- 
tion?    3.    Describe  briefly  the  process  for  determining  the  acidity  of  - 
lemon  juice.     4.  What  per  cent  of  acidity  did  you  obtain?     5.   How 
does  this  compare  with  the  acidity  of  vinegar? 

Experiment  No.  6 
Influence  of  Heat  on  Potato  Starch  Grains 

v  With  the  point  of  a  knife  scrape  slightly  the  surface  of  a  raw 
potato  and  place  a  drop  of  the  starchy  juice  upon  the  microscopi- 
cal slide.  Cover  with  cover  glass  and  examine  under  the  micro- 
scope. 

In  the  evaporating  dish  cook  a  small  piece  of  potato,  then  place  a 
very  small  portion  upon  the  slide,  and  examine  with  the  microscope. 

Make  drawings  of  the  starch  grains  in  raw  and  in  cooked  potatoes. 

Experiment  No.  7 
Influence  of  Yeast  on  Starch  Grains 

Moisten  a  small  portion  of  the  dough  prepared  with  yeast  and 
with  the  stirring  rod  place  a  drop  of  the  starchy  water  upon  the 
slide.  Cover  with  cover  glass  and  examine  under  the  micro- 
scope. 

Repeat,  examining  a  drop  of  starchy  water  washed  from  flour. 

Make  drawing  of  wheat  starch  grain  in  flour  and  in  dough  pre- 
pared with  yeast. 


LABORATORY    PRACTICE  307 

Experiment  No.  8 
Mechanical  Composition  of  Potatoes 

Wash  one  potato.  Weigh,  then  peel,  making  the  peeling  as  thin 
as  possible.  Weigh  the  peeled  potato  and  weigh  the  peeling  or 
refuse.  Calculate  the  per  cent  of  potato  that  is  edible  and  the  per 
cent  that  is  refuse. 

Experiment  No.  9 
Pectose  from  Apples 

Reduce  a  small  peeled  apple  to  a  pulp.  Squeeze  the  pulp  through 
a  clean  cloth  into  a  beaker.  Add  10  cc.  H2O  and  heat  on  a  sand 
bath  to  coagulate  the  albumin.  Filter,  adding  a  little  hot  water  if 
necessary.  To  the  filtrate  add  5  cc.  alcohol.  The  precipitate  is 
the  pectose  material. 

i.  Is  the  pectose  from  the  apple  soluble?  2.  Is  it  coagulated  by 
heat?  3.  Is  it  soluble  in  alcohol? 

Experiment  No.  10 
Lemon  Extract 

To  5  cc.  of  the  extract  in  a  test  tube  add  an  equal  volume  of 
water.  A  cloudy  appearance  indicates  the  presence  of  lemon  oil. 
If  the  solution  remains  clear  after  adding  the  water,  the  extract  does 
not  contain  lemon  oil. 

Why  does  the  extract  containing  lemon  oil  become"  cloudy  on 
adding  water? 

Experiment  No.  n 
Vanilla  Extract 

Pour  into  a  test  tube  5  cc.  of  the  extract  to  be  tested.  Evaporate 
to  one  third.  Then  add  sufficient  water  to  restore  the  original  vol- 
ume. If  a  brown,  flocculent  precipitate  is  formed,  the  sample  con- 
tains pure  vanilla  extract.  Resin  is  present  in  vanilla  beans  and  is 
extracted  in  the  essence.  The  resin  is  readily  soluble  in  50  per  cent 


308       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

alcohol.  If  the  alcohol  is  removed  from  the  extract,  the  excess  of 
resin  is  precipitated,  or  if  free  from  alkali,  it  may  be  precipitated  by 
diluting  the  original  solution  with  twice  its  volume  of  water.  Test 
the  two  samples  and  compare. 

(Adapted  from  Leach,  "  Food  Inspection  and  Analysis.") 

I.  Describe  the  appearance  of  each  sample  after  evaporating  and 
adding  water.  2.  Which  sample  contains  pure  vanilla  extract? 
3.  State  the  principle  underlying  this  test. 

Experiment  No.  12 
Testing  Olive  Oil  for  Cotton  Seed  Oil 

Pour  into  a  test  tube  5  cc.  of  the  oil  to  be  tested  and  5  cc.  of 
Halphen^  Reagent.  Mix  thoroughly.  Plug  the  test  tube  loosely 
with  cotton,  and  heat  in  a  bath  of  boiling  saturated  brine  for  15 
minutes.  If  cotton  seed  oil  is  present,  a  deep  red  or  orange  color  is 
produced.  Test  two  samples  and  compare. 

Halphen's  Reagent.  —  Mix  equal  volumes  of  amyl  alcohol  and  car- 
bon disulphid  containing  about  one  per  cent  of  sulphur  in  solution. 
(Adapted  from  Leach,  "  Food  Inspection  and  Analysis.") 

Experiment  No.  13 
Testing  for  Coal  Tar  Dyes 

Dilute  20  to  30  cc.  of  the  material  to  100  cc. ;  boil  for  10  minutes 
with  10  cc.  of  a  10  per  cent  solution  of  potassium  bisulphate  and 
a  piece  of  white  woolen  cloth  which  has  previously  been  boiled  in 
a  o.i  per  cent  solution  of  NaOH  and  thoroughly  washed  in  water. 
Remove  the  cloth  from  the  solution,  wash  in  boiling  water,  and  dry 
between  pieces  of  filter  paper.  A  bright  red  indicates  coal  tar  dye. 
If  the  coloring  matter  is  entirely  from  fruit,  the  woolen  cloth  will  be 
either  uncolored  or  will  have  a  faint  pink  or  brown  color  which  is 
changed  to  green  or  yellow  by  ammonia  and  is  not  restored  by 
washing.  This  is  the  Arata  test. 

(Adapted,  Winston,  Conn.  Experiment  Station  Report.) 


LABORATORY   PRACTICE  309 

i.  Describe  Arata's  wool  test  for  coal  tar  dyes.  2.  What  is  the 
appearance  of  the  woolen  cloth  when  the  coloring  matter  is  entirely 
from  fruit  ?  3.  What  effect  has  NH4OH  upon  the  color  ?  4.  Why 
is  NaOH  used  ?  5.  Why  may  not  cotton  cloth  be  used  instead  of 
woolen  ?  6.  What  can  you  say  of  the  use  of  coal  tar  dyes  in  foods  ? 

Experiment  No.   14 
Determining  the  Per  Cent  of  Skin  in  Beans 

Place  in  an  evaporating  dish  10  gm.  of  beans,  50  cc.  of  water, 
and  |  gm.  of  baking  soda.  Boil  10  minutes  or  until  the  skins  are 
loosened,  then  drain  off  the  water.  Add  cold  water  and  rub  the 
beans  together  till  the  skins  slip  off.  Collect  the  skins,  place  on  a 
watch  glass  and  dry  in  the  water  oven  for  \  hour.  Weigh  the  dried 
skins  and  calculate  the  per  cent  of  "  skin." 

i.  What  does  the  soda  do?  2.  What  effect  would  hard  lime- 
water  have  upon  the  skins  ?  3.  How  does  removal  of  skins  affect 
food  value  of  beans  and  digestibility  ? 

Experiment  No.  15 
Extraction  of  Fat  from  Peanuts 

L^- 

Shell  three  or  four  peanuts  and  with  the  mortar  and  pestle  break 
them  into  small  pieces.  Place  in  a  test  tube  and  pour  over  them 
about  10  cc.  of  ether.  Cork  the  test  tube  and  allow  it  to  stand  30 
minutes,  shaking  occasionally.  Filter  on  to  a  watch  glass  and  let 
stand  until  the  ether  evaporates,  and  then  observe  the  fat. 

i.  What  is  the  appearance  of  the  peanut  fat  ?  2.  What  is  the 
solvent  of  the  fat  ?  3.  What  becomes  of  the  ether  ?  4.  Why 
should  the  peanuts  be  broken  into  small  pieces  ? 

Experiment  No.  16 
Microscopic  Examination  of  Milk 

Place  a  drop  of  milk  on  a  microscopical  slide  and  cover  with  cover 
glass.  Examine  the  milk  to  detect  impurities,  as  dust,  hair,  refuse, 
etc.  Make  drawings  of  any  foreign  matter  present. 


310       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

Experiment  No.  17 
Formaldehyde  in  Cream  or  Milk 

To  10  cc.  of  milk  in  a  casserole  add  10  cc.  of  the  acid  reagent. 
Heat  slowly  over  the  flame  nearly  to  boiling,  holding  the  casserole 
in  the  hand  and  giving  it  a  slight  rotary  movement  while  heating. 
The  presence  of  formaldehyde  is  indicated  by  a  violet  coloration 
varying  in  depth  with  the  amount  present.  In  the  absence  of 
formaldehyde  the  solution  slowly  turns  brown. 

Acid  Reagent.  —  Commercial  hydrochloric  acid  (sp.gr.  1.2)  con- 
taining 2  cc.  per  liter  of  10  per  cent  ferric  chlorid. 

(Adapted  from  Leach,  "  Food  Inspection  and  Analysis.") 

I.  How  may  the  presence  of  formaldehyde  in  milk  be  detected  ? 
2.  Why  in  this  test  is  it  necessary  to  use  acid  containing  ferric 
chlorid  ?  3.  Describe  the  appearance  of  the  two  samples  of  milk 
after  adding  the  acid  reagent  and  heating.  4.  Which  sample 
showed  the  presence  of  formaldehyde  ? 

Experiment  No.  18 
Gelatine  in  Cream  or  Milk 

To  20  cc.  of  milk  or  cream  in  a  beaker  add  20  cc.  of  acid  mercuric 
nitrate  and  about  40  cc.  of  H2O.  Let  stand  for  a  few  minutes  and 
filter.  Filtrate  will  be  cloudy  if  gelatine  is  present. 

Add  £  cc.  of  a  dilute  solution  of  picric  acid  —  a  heavy  yellow 
precipitate  indicates  gelatine. 

Acid  Mercuric  Nitrate.  —  i  part  by  weight  of  Hg,  2  parts  HNO3 
(sp.  gr.  1.42).  Dilute  25  times  with  water. 

Experiment  No.  19 
Testing  for  Oleomargarine 

Apply  the  following  tests  to  two  samples  of  the  material : 
Boiling  or  Spoon  Test.  —  Melt  the  sample  to  be  tested  —  a  piece 
about  the  size   of  a  chestnut  —  in  a  large  spoon,  hastening   the 


LABORATORY   PRACTICE  311 

process  by  stirring  with  a  splinter.  Then,  increasing  the  heat, 
bring  to  as  brisk  a  boil  as  possible  and  stir  thoroughly,  not  neglect- 
ing the  outer  edges.  Oleomargarine  and  renovated  butter  boil 
noisily,  sputtering  like  a  mixture  of  grease  and  water,  and  produce 
no  foam,  or  but  very  little.  Genuine  butter  boils  with  less  noise  and 
produces  an  abundance  of  foam. 

Waterhouse  Test.  —  Into  a  small  beaker  pour  50  cc.  of  sweet 
milk.  Heat  nearly  to  boiling  and  add  from  5  to  10  gms.  of  butter 
or  oleomargarine.  Stir  with  a  glass  rod  until  fat  is  melted.  Then 
place  the  beaker  in  cold  water  and  stir  the  milk  until  the  tempera- 
ture falls  sufficiently  for  the  fat  to  congeal.  At  this  point  the  fat,  if 
oleomargarine,  can  easily  be  collected  into  one  lump  by  means  of 
the  rod  ;  while  if  butter,  it  will  granulate-  and  cannot  be  collected. 
(From  Farmers'  Bui.  131,  U.  S.  Dept.  of  Agriculture.) 

I.  Name  two  simple  tests  for  distinguishing  butter  and  oleomar- 
garine. 2.  Describe  these  tests.  3.  Why  do  butter  and  oleomar- 
garine respond  differently  to  these  tests?  4.  Are  these  tests  based 
upon  chemical  or  physical  properties  of  the  fats  ? 

Experiment  No.  20 
Testing  for  Watering  or  Skimming  of  Milk 

a.  Fat  Content  of  Milk  by  Means  of  Babcock  Test.  —  Measure 
with  pipette  into  test  bottle  17.6  cc.  of  milk.      Sample  should  be 
carefully  taken   and  well    mixed.     Measure  with   cylinder  17.5  cc. 
commercial  H2SO4  and  add  to  milk  in  test  bottle.     (See  Fig.  25.) 
Mix  acid  and  milk  by  rotating  the  bottle.     Then  place  test  bottles 
in  centrifugal  machine   and  whirl  5  minutes.     Add   sufficient   hot 
water  to  test  bottles  to  bring  contents  up  to  about  the  8th  mark  on 
stem.     Then  whirl  bottles  2  minutes  longer  and  read  fat.     Read 
from  extreme  lowest  to  highest  point.     Each  large  division  as  I  to  2 
represents  a  whole  per  cent,  each  small  division  0.2  of  a  per  cent. 

b.  Determining  Specific  Gravity  by  Means  of  Lactometer.  —  Pour 
150  cc.  of  milk  into  200  cc.  cylinder.     Place  lactometer  in  milk  and 


312       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

note  depth  to  which  it  sinks  as  indicated  on  stem.  Note  also  tem- 
perature of  milk.  For  each  10°  above  60°  F.  add  i  to  the  lactometer 
number,  in  order  to  make  the  necessary  correction  for  temperature. 
For  example,  if  milk  has  sp.  gr.  of  1.032  at  temperature  of  70°,  it 
will  be  equivalent  to  sp.  gr.  of  1.033  at  60°.  Ordinarily  milk  has  a 
sp.  gr.  of  1.029  to  I-°34-  If  milk  has  sp.  gr.  of  less  than  1.029,  or 
contains  less  than  3  per  cent  fat,  it  may  be  considered  watered  milk. 
If  the  milk  has  a  high  sp.  gr.  (above  1.035)  and  a  low  content  of 
fat,  some  of  the  fat  has  been  removed. 

(For  extended  direction  for  milk  testing  see  Snyder's  "  Dairy  Chemistry.") 

Experiment  No.  21 
Boric  Acid  in  Meat 

Cut  into  very  small  pieces  5  gms.  of  meat,  removing  all  the  fat 
possible.  Place  in  an  evaporating  dish  with  20  to  25  cc.  of  water 
to  which  a  few  drops  of  HC1  have  been  added  and  warm  slightly. 
Dip  a  piece  of  turmeric  paper  in  the  meat  extract  and  dry.  A  rose- 
red  color  of  the  turmeric  paper  after  drying  (turned  olive  by  a  weak 
ammonia  solution)  is  indicative  of  boric  acid. 

i.  How  may  meat  be  tested  for  boric  acid?  2.  Why  is  HC1 
added  to  the  water?  3.  Why  is  the  water  containing  the  meat 
warmed  slightly?  4.  What  is  the  appearance  of  the  turmeric  paper 
after  being  dipped  in  the  meat  extract  and  dried?  5.  What  change 
takes  place  when  it  is  moistened  with  ammonia,  and  why? 

Experiment  No.  22 
Microscopic  Examination  of  Cereal  Starch  Grains 

Make  a  microscopic  examination  and  drawings  of  wheat,  corn, 
rice,  and  oat  starch  grains,  comparing  them  with  the  drawings  of  the 
different  starch  grains  on  the  chart.  If  the  material  is  coarse,  pul- 
verize in  a  mortar  and  filter  through  cloth.  Place  a  drop  or  two  of 
the  starchy  water  on  the  slide,  cover  with  a  cover  glass,  and  ex- 
amine. 


LABORATORY   PRACTICE  313 

Experiment  No.   23 
Identification  of  Commercial  Cereals 

Examine  under  the  microscope  two  samples  of  cereal  breakfast 
foods,  and  by  comparison  with  the  wheat,  corn,  and  oat  starch  grains 
previously  examined  tell  of  what  grains  the  breakfast  foods  are  made 
and  their  approximate  food  value. 

Experiment  No.   24 
Granulation  and  Color  of  Flour 

Arrange  on  glass  plate,  in  order  of  color,  samples  of  all  the  differ- 
ent grades  of  flour.  Note  the  differences  in  color.  How  do  these 
differences  correspond  with  the  grades  of  the  flour?  Examine  the 
flour  with  a  microscope,  noting  any  coarse  or  dark-colored  particles  of 
bran  or  dust.  Rub  some  of  the  flour  between  the  thumb  and  fore- 
finger. Note  if  any  granular  particles  can  be  detected. 

Experiment  No.  25 
Capacity  of  Flour  to  absorb  Water 

Weigh  out  15  gms.  of  soft  wheat  flour  into  an  evaporating  dish; 
then  add  from  burette  a  measured  quantity  of  water  sufficient  to  make 
a  stiff  dough.  Note  the  amount  of  water  required  for  this  purpose. 
Repeat  the  operation,  using  hard  wheat  flour. 

i.  How  may  the  absorptive  power  of  a  flour  be  determined?  2.  To 
what  is  it  due?  3.  Why  do  some  flours  absorb  more  water  than 
others  ? 

Experiment  No.   26 
Acidity  of  Flour 

Weigh  into  a  flask  20  gms.  of  flour  and  add  200  cc.  distilled 
water.  Shake  vigorously.  After  letting  stand  30  minutes,  filter  and 
then  titrate  50  cc.  of  the  filtrate  against  standard  KOH  solution, 
using  phenolphthalein  as  indicator.  I  cc.  of  the  alkali  equals  0.009 
gms.  lactic  acid.  Calculate  the  per  cent  of  acid  present. 


314       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

I.  How  may  the  acidity  of  a  flour  be  determined?  2.  The  acid- 
ity is  expressed  in  percentage  amounts  of  what  acid?  3.  What  per 
cent  of  acidity  is  found  in  normal  flours?  4.  What  does  a  high 
acidity  of  a  flour  indicate  ? 

Experiment  No.  27 
Moist  and  Dry  Gluten 

Weigh  30  gm.  of  flour  into  a  porcelain  dish.  Make  the  flour  into 
a  stiff  dough.  After  30  minutes  obtain  the  gluten  by  washing,  being 
careful  to  remove  all  the  starch  and  prevent  any  losses.  Squeeze  the 
water  from  the  gluten  as  thoroughly  as  possible.  Weigh  the  moist 
gluten  and  calculate  the  per  cent.  Dry  the  gluten  in  the  water  oven 
and  calculate  the  per  cent  of  dry  gluten. 

Experiment  No.  28 
Gliadin  from  Flour 

Place  in  a  flask  10  gms.  of  flour,  30  cc.  of  alcohol,  and  20  cc.  of 
water.  Cork  the  flask  and  shake,  and  after  a  few  minutes  shake 
again.  Allow  the  alcohol  to  act  on  the  flour  for  an  hour,  or  until 
the  next  day.  Then  filter  off  the  alcohol  solution  and  evaporate  the 
filtrate  to  dryness  over  the  water  bath.  Examine  the  residue  ;  to  a 
portion  add  a  little  water ;  burn  a  small  portion  and  observe  odor. 

i.  Describe  the  appearance  of  the  gliadin.  2.  What  was  the  re- 
sult when  water  was  added?  3.  When  burned,  what  was  the  odor  of 
the  gliadin,  and  what  does  this  indicate  ?  4.  What  is  gliadin  ? 

Experiment  No.  29 
Bread-making  Test 

Make  a  "  sponge  "  by  mixing  together : 
12  gm.  sugar, 

12  gm.  yeast  (compressed), 
4  gm.  salt, 
175  cc.  water  (temp.  32°  C.). 


LABORATORY   PRACTICE  315 

Let  stand  J  hour  at  a  temperature  of  30°  C.  In  a  large  bowl,  mix 
with  a  knife  or  spatula  7.7  gms.  of  lard  with  248.6  gms.  of  flour. 
Then  add  160  cc.  of  the  "  sponge,"  or  as  much  as  is  needed  to  make 
a  good  stiff  dough,  and  mix  thoroughly,  using  the  spatula.  With 
some  flours  as  small  a  quantity  as  150  cc.  of  sponge  may  be  used. 
If  more  moisture  is  necessary,  add  H2O.  Keep  at  temperature  of 
30°  C.  Allow  the  dough  to  stand  50  minutes  to  first  pulling,  40  min- 
utes to  second  pulling,  and  30  to  50  minutes  to  the  pan.  Let  it  rise 
to  top  of  pan  and  then  bake  for  1  hour  in  an  oven  at  a  temperature 
of  1 80°  C.  One  loaf  of  bread  is  made  of  patent  flour  of  known 
quality  as  a  standard  for  comparison,  and  other  loaves  of  the  flours 
to  be  tested.  Compare  the  loaves  as  to  size  (cubic  contents),  color, 
porosity,  odor,  taste,  nature  of  crust,  and  form  of  loaf. 

Experiment  No.  30 
Microscopic  Examination  of  Yeast 

On  a  watch  glass  mix  thoroughly  a  very  small  piece  of  yeast  with 
about  5  cc.  of  water  and  then  with  the  stirring  rod  place  a  drop 
of  this  solution  on  the  microscopical  slide,  adding  a  drop  of  very 
dilute  methyl  violet  solution.  Cover  with  the  cover  glass  and 
examine  under  the  microscope.  The  living  activ.e  cells  appear  color- 
less while  the  decayed  and  lifeless  ones  are  stained.  Yeast  cells  are 
circular  or  oval  in  shape.  (See  Fig.  46.) 

(Adapted  from  Leach,  "  Food  Inspection  and  Analysis.") 

Experiment  No.  31 
Testing  Baking  Powders  for  Alum 

Place  about  2  gms.  of  flour  in  a  dish  with  \  gm.  baking  powder. 
Add  enough  water  to  make  a  dough  and  then  2  or  3  drops  of  tincture 
of  logwood  and  2  or  3  drops  of  ammonium  carbonate  solution.  Mix 
well  and  observe  ;  a  blue  color  indicates  alum.  Try  the  same  test, 
using  flour  only  for  comparison. 


. 


316       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

i.  How  do  you  test  a  baking  powder  for  alum?  2.  What  differ- 
ence in  color  did  you  observe  in  the  test  with  the  baking  powder 
containing  alum  and  in  that  with  the  flour  only?  3.  Why  is  the 
(NH4)2CO3  solution  used? 

Experiment  No.  32 
Testing  Baking  Powders  for  Phosphoric  Acid 

Dissolve  \  gm.  of  baking  powder  in  5  cc.  of  H2O  and  3  cc. 
HNO3.  Filter  and  add  3  cc.  ammonium  molybdate.  Heat  gently. 
A  yellow  precipitate  indicates  phosphoric  acid. 

i.  How  do  you  test  a  baking  powder  for  phosphoric  acid? 
2.  What  is  the  yellow  precipitate  obtained  in  this  test? 

Experiment  No.  33 
Testing  Baking  Powders  for  Ammonia 

Dissolve  \  gm.  of  material  in  10  cc.  water;  filter  off  any  in- 
soluble residue  and  to  the  filtrate  add  2  or  3  cc.  NaOH  and  apply 
heat.  Test  the  gas  given  off  with  moistened  turmeric  paper.  If 
NHs  is  present,  the  paper  will  be  colored  brown.  Do  not  allow  the 
paper  to  come  in  contact  with  the  liquid  or  sides  of  the  test  tube. 
(Perform  the  tests  on  two  samples  of  baking  powder.) 

i.  How  do  you  test  a  baking  powder  for  ammonia?  2.  Why  do 
you  add  NaOH  ?  3.  Why  must  you  be  careful  not  to  let  the  tur- 
meric paper  touch  the  sides  of  the  test  tube  or  the  liquid  ? 

Experiment  No.  34 
Vinegar  Solids 

Into  a  weighed  aluminum  or  porcelain  dish  pour  10  cc.  of  vinegar. 
Weigh  and  then  evaporate  over  boiling  water.  To  drive  off  the  last 
traces  of  moisture  dry  in  the  water  oven  for  an  hour.  Cool  and 
weigh.  Calculate  the  per  cent  of  solids.  Observe  the  appearance 
of  the  solids.  Test  both  samples  and  compare. 


LABORATORY    PRACTICE  317 

I.  How  may  the  per  cent  of  solids  in  vinegar  be  determined? 
2.  Describe  the  appearance  of  the  solids  from  the  good  and  from 
the  poor  sample  of  vinegar.  3.  What  is  the  legal  standard  for 
vinegar  solids  in  your  state? 

Experiment  No.  35 
Specific  Gravity  of  Vinegar 

Pour  170  cc.  vinegar  into  200  cc.  cylinder.  Place  a  hydrometer 
for  heavy  liquids  (sp.  gr.  I  to  i.i)  in  the  cylinder.  Note  the  depth 
to  which  it  sinks  and  the  point  registered  on  the  scale  on  the  stem. 
Note  temperature  of  vinegar.  Record  specific  gravity  of  vine- 
gar. 

i.  What  effect  would  addition  of  water  to  vinegar  have  upon  its 
specific  gravity?  2.  What  effect  would  addition  of  such  material 
as  sugar  have  upon  specific  gravity?  3.  Why  should  the  specific 
gravity  of  vinegar  be  fairly  constant?  4.  What  would  be  the  weight 
of  1000  cc.  of  vinegar  calculated  from  the  specific  gravity? 

Experiment  No.  36 
Acidity  of  Vinegar 

Into  a  small  beaker  pour  6  cc.  of  vinegar  and  10  cc.  of  water  and 
a  few  drops  of  phenolphthalein  indicator.  Run  in  standard  KOH 
solution  from  a  burette  until  a  faint  pink  tinge  remains  permanently. 
Note  the  number  of  cubic  centimeters  of  KOH  solution  required 
to  neutralize  the  acid.  Divide  this  number  by  10,  which  will  give 
approximately  the  per  cent  of  acetic  acid. 

i.  How  may  the  per  cent  of  acidity  of  vinegar  be  determined? 
2.  Why  was  phenolphthalein  used?  3.  Why  was  KOH  used? 
4.  What  acids  does  vinegar  contain?  5.  What  is  the  legal  re- 
quirement in  this  state  for  acetic  acid  in  vinegar?  6.  How 
did  the  acidity  you  obtained  compare  with  this  legal  require- 
ment? 


318       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

Experiment  No.  37 
Deportment  of  Vinegar  with  Reagents 

To  10  cc.  of  vinegar  in  a  test  tube  add  8  or  10  drops  of  lead 
sub-acetate  and  shake.  Observe  the  precipitate.  Lead  sub-acetate 
precipitates  mainly  the  malic  acid  which  is  always  present  in  cider 
vinegar. 

I.  How  may  the  presence  of  malic  acid  in  a  vinegar  be  detected? 
2.  Describe  the  precipitate.  3.  What  does  malic  acid  in  a  vinegar 
indicate? 

Experiment  No.  38 

Testing  Mustard  for  Turmeric 

Place  i  gm.  of  ground  mustard  on  a  small  watch  glass  and  moisten 
slightly  with  water.  Add  2  or  3  drops  of  NH4OH,  stirring  well 
with  a  glass  rod.  A  brown  color  indicates  turmeric  present  in  con- 
siderable quantity. 

Test  a  sample  of  good  mustard  and  one  adulterated  with  turmeric 
and  compare  the  results. 

Experiment  No.  39 
Examination  of  Tea  Leaves 

Soak  a  small  amount  of  tea  and  unroll  8  or  10  of  the  leaves. 
Make  a  drawing  of  a  tea  leaf.  Observe  the  proportion  of  stems  in 
each  of  three  samples  of  tea ;  also  the  relative  proportion  of  large 
and  small  leaves.  Observe  if  the  leaves  are  even  as  to  size  and 
of  a  uniform  color. 

Experiment  No.  40 
Action  of  Iron  Compounds  upon  Tannic  Acid 

Make  an  infusion  of  tea  by  placing  3  gms.  of  tea  in  loocc.  of  hot 
water  and  stirring  well.  Filter  off  some  of  the  infusion  and  test 
5  cc.  with  ferrous  sulphate  solution  made  by  dissolving  I  gm. 
FeSO4  in  10  cc.  H2O  and  filtering.  Note  the  result. 


LABORATORY   PRACTICE  319 

i .  What  change  in  color  did  you  observe  when  the  ferrous  sul- 
phate solution  was  added  to  the  tea  infusion  ?  2.  What  effect 
would  waters  containing  iron  have  upon  the  tea  infusion? 

Experiment  No.  41 
Identification  of  Coffee  Berries 

Examine  Rio,  Java,  and  Mocha  coffee  berries.  Describe  each. 
Note  the  characteristics  of  each  kind  of  coffee  berry. 

Experiment  No.  42 
*•    Detecting  Chicory  in  Coffee 

Fill  a  beaker  with  water  and  place  about  a  teaspoonful  of  ground 
coffee  on  the  surface.  If  much  of  the  ground  material  sinks  and  it 
imparts  a  dark  brown  color  to  the  lower  portion  of  the  liquid,  it  is 
an  indication  of  the  presence  of  chicory.  Pure  coffee  floats  on 
water.  Chicory  has  a  higher  specific  gravity  than  coffee. 

i.  How  may  the  presence  of  chicory  in  ground  coffee  be  de- 
tected? 2.  Why  does  coffee  float  on  the  water  while  chicory  sinks? 
3.  What  effect  does  chicory  have  upon  the  color  of  water? 

Experiment  No.  43 
Testing  Hard  and  Soft  Waters 

Partially  fill  a  large  cylinder  with  very  hard  water.  This  may  be 
prepared  by  dissolving  o.  I  to  0.2  gm.  calcium  chloride  in  500  cc. 
of  ordinary  water.  Add  to  this  a  measured  quantity  of  soap  solu- 
tion. Mix  well  and  notice  how  many  cubic  centimeters  of  soap  so- 
lution must  be  used  before  a  permanent  lather  is  formed,  also  notice 
the  precipitate  of  "lime  soap."  Repeat  this  experiment,  using 
either  rain  or  distilled  water,  and  compare  the  cubic  centimeters  of 
soap  solution  used  with  that  in  former  test.  Repeat  the  test,  using 
tap  water. 

Soap  Solution. — Scrape  10  gms.  of  castile  soap  into  fine  shavings 


320       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

and  dissolve  in  a  liter  of  alcohol,  dilute  with  }  water.     Filter  if  not 
clear  and  keep  in  a  tightly  stoppered  bottle. 

I.  Why  is  more  soap  required  to  form  a  lather  with  hard  water 
than  with  soft  water?  2.  What  is  meant  by  "lime  soap"?  De- 
scribe its  appearance.  3.  How  may  hard  waters  be  softened  for 
household  purposes? 

Experiment  No.  44 
Solvent  Action  of  Water  on  Lead 

Put  i  gm.  of  clean  bright  lead  shavings  i-nto  a  test  tube  contain- 
ing 10  cc.  of  distilled  water.  After  24  hours  decant  the  clear  liquid 
into  a  second  test  tube,  acidify  slightly  with  HCL,  and  add  a  little 
hydrogen  sulphid  water.  A  black  or  brownish  coloration  indicates 
lead  in  solution. 

(Adapted  from  Caldwell  and  Breneman,  "Introductory  Chemical  Practice.") 
Under  what  conditions  may  lead  pipes  be  objectionable? 

Experiment  No.  45 
Suspended  Matter  in  Water 

Place  a  drop  of  water  on  the  microscopical  slide,  cover  with  cover 
glass,  and  examine  with  the  microscope.  Note  the  occurrence  and 
appearance  of  any  suspended  matter  in  the  water. 

Experiment  No.  46 
Organic  Matter  in  Water 

Pour  into  the  evaporating  dish  100  cc.  H2O  and  evaporate  to 
dryness  over  the  sand  bath.  Ignite  the  solids.  If  the  solids  blacken 
when  ignited,  the  water  contains  organic  matter. 

Experiment  No.  47 
Deposition  of  Lime  by  Boiling  Water 

Boil  for  a  few  minutes  about  200  cc.  of  water  in  a  flask.  After 
the  water  is  cool,  note  any  sediment  of  lime  or  turbidity  of  the  water 
due  to  expelling  the  carbon  dioxid. 


LABORATORY    PRACTICE  321 

i.  What  is  meant  by  a  "hard"  water?  2.  What  do  the  terms 
"  temporary  "  and  "  permanent "  hardness  of  water  mean  ?  3.  What 
acts  as  a  solvent  of  the  lime  in  water?  4.  Why  does  boiling  cause 
the  lime  to  be  deposited  ? 

Experiment  No.  48 
Qualitative  Tests  for  Minerals  in  Water 

Test  for  Chlorids.  —  To  10  cc.  of  H2O  add  a  few  drops  of  HNO3 
and  2  cc.  of  AgNO3.  A  white  precipitate  indicates  the  presence 
of  chlorids,  usually  in  the  form  of  sodium  chlorid. 

Test  for  Sulphates.  — To  10  cc.  of  water  add  2  cc.  of  dilute  HC1 
and  2  cc.  of  BaCl2.  A  cloudiness  or  the  formation  of  a  white  pre- 
cipitate indicates  the  presence  of  sulphates. 

Test  for  Iron.  —  If  a  brown  sediment  is  formed  in  water  exposed 
to  the  air  for  some  time,  it  is  probably  iron  hydroxid.  To  10  cc.  of  the 
water  add  a  few  drops  of  HNO3,  heat,  and  then  add  J  cc.  of 
NH4CNS.  A  red  color  indicates  the  presence  of  iron. 

Test  for  CaO  and  MgO.  —  To  10  cc.  of  H2O  add  5  cc.  NH4OH. 
If  a  precipitate  forms,  filter  it  off,  and  to  the  filtrate  add  3  cc.  NH4C1 
and  5  cc.  (NH4)2C2O4.  The  precipitate  is  CaC2O4,  and  the  filtrate 
contains  the  magnesia.  Filter  and  add  5  cc.  Na3PO4  to  precipitate 
MgNH4P04. 

i .  How  would  you  test  a  water  to  detect  the  presence  of  organic 
matter?  2.  Name  some  mineral  impurities  often  found  in  water. 
3.  Describe  the  test  for  chlorids  ;  for  sulphates  ;  for  iron ;  for  lime ; 
for  magnesium.  4.  Of  the  two  classes  of  impurities  found  in  water, 
which  is  the  more  harmful?  5.  Name  three  ways  of  purifying 
waters  known  to  be  impure,  and  tell  which  is  the  most  effectual. 

Experiment  No.  49 
Testing  for  Nitrites  in  Water 

To  50  cc.  of  water  in  a  small   beaker  add  with  a  pipette  2  cc. 
of  naphthylamine  hydrochloride  and  then  2  cc.  of  sulphanilic  acid. 
Y 


322       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

Stir  well  and  wait  20  minutes  for  color  to  develop.     A  pink  color  in- 
dicates nitrites. 

REAGENTS  USED 

Sulphanilic  Acid.  —  Dissolve  5  gm.  in  150  cc.  of  dilute  acetic 
acid;  sp.  gr.  1.04. 

Naphthylamine  Hydrochloride.  —  Boil  o.i  gm.  of  solid  a-amido- 
naphthaline  (naphthylamine)  in  20  cc.  of  water,  filter  the  solution 
through  a  plug  of  absorbent  cotton,  and  mix  the  filtrate  with  180  cc. 
of  dilute  acetic  acid.  All  water  used  must  be  free  from  nitrites,  and 
all  vessels  must  be  rinsed  out  with  such  water  before  tests  are  applied. 

I.  Would  a  water  showing  the  presence  of  nitrites  be  a  safe  drink- 
ing water?  Why?  2.  What  are  nitrites?  3.  What  does  the  pres- 
ence of  nitrites  indicate?  4.  Are  small  amounts  of  nitrites,  when 
not  associated  with  bacteria,  injurious  ? 


REVIEW  QUESTIONS 

CHAPTER  I 

GENERAL  COMPOSITION  OF  FOODS 

I.  To  what  extent  is  water  present  in  foods?  2.  What  foods 
contain  the  most,  and  what  foods  the  least  water?  3.  How  does  the 
water  content  of  some  foods  vary  with  the  hydroscopicity  of  the  air? 

4.  How  may  changes  in  water  content  of  foods  affect  their  weight  ? 

5.  Why  is  it  necessary  to  consider  the  water  content  of  foods  in 
assigning  nutritive  values  ?     6.    How  is  the  dry  matter  of  a  food  de- 
termined?    7.    Why  is  the  determination  of  the  water  in  a  food  often 
a  difficult  process  ?     8.    What  is  the  ash  or  mineral  matter  of  a  food? 
9.    How  is  it  obtained?     10.   What  is  its  source?     11.    Of  what  is 
the  ash  of  plants  composed?     12.    What  part  in  plant  life  do  these 
ash  elements  take?     13.    Name  the  ash  elements  essential  for  plant 
growth.     14.   Which  of  the  mineral  elements  take  the  most  essential 
part  in  animal   nutrition?     15.    In  what   form   are   these   elements 
usually  considered  most  valuable?     16.   Why  is  sodium  chloride  or 
common  salt  necessary  for  animal  life?     17.    How  do  food  materials 
differ  in  ash  content  ?     18.  Define  organic  matter  of  foods.     19.  How 
is  it  obtained?     20.    Of  what  is  it  composed?     21.    Into  what  is  the 
organic  matter  converted  when  it  is  burned?       22.    Give  the  two 
large    classes    of  organic    compounds    found    in    food    materials. 
23.    Name  the  various   subdivisions   of  the   non-nitrogenous  com- 
pounds.    24.   What  are  the  carbohydrates?     25.    Give  their  general 
composition.       26.    What  is   cellulose?      27.   Where  is   it   found? 
28.   What  is  its  function  in  plants?     29.    What  is  its  food  value? 
30.    In  what  way  may  cellulose  be  of  value  in  a  ration?     31.    In  what 
way  may  it  impart  a  negative  value  to  a  ration  ?     32.    What  is  starch  ? 

323 


324       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

33.  Where  is  it  mainly  found  in  plants?  34.  Give  the  mechanical 
structure  of  the  starch  grain.  35.  Why  is  starch  insoluble  in  cold 
water?  36.  How  do  starch  grains  from  different  sources  differ 
in  structure?  37.  What  effect  does  heat  have  upon  starch? 
38.  Define  hydration  of  starch.  39.  Under  what  conditions  does 
this  change  take  place?  40.  What  value  as  a  nutrient  does  starch 
possess?  41.  What  is  sugar?  42.  How  does  it  resemble  and 
how  differ  in  composition  from  starch  ?  43.  What  are  the  pectose 
substances?  44.  How  are  they  affected  by  heat?  45.  What 
food  value  do  they  possess?  46.  What  is  nitrogen-free-extract? 
47.  How  is  it  obtained?  48.  How  may  the  nitrogen-free-extract 
of  one  food  differ  from  that  of  another?  49.  What  are  the  fats? 
50.  How  do  they  differ  in  composition  from  the  starches  ?  51.  Why 
does  fat  when  burned  or  digested  produce  more  heat  than  Starch 
or  sugar?  52.  Name  the  separate  fats  of  which  animal  and  vege- 
table foods  are  composed.  53.  Give  some  of  the  physical  character- 
istics of  fat.  54.  What  is  the  iodine  absorption  number  of  a  fat? 
55.  How  does  the  specific  gravity  of  fat  compare  with  that  of 
water?  56.  Into  what  two  constituents  may  all  fats  be  separated? 
57.  What  is  ether  extract?  58.  How  does  the  ether  extract  in  fats 
vary  in  composition  and  nutritive  value?  59.  What  are  the  organic 
acids?  60.  Name  those  most  commonly  met  with  in  foods. 
61.  What  nutritive  value  do  they  possess  ?  62.  What  dietetic  value? 
63.  What  value  are  they  to  the  growing  plant?  64.  What  organic 
acids  are  found  in  animal  foods?  65.  What  are  the  essential  oils? 
66.  How  do  they  differ  from  the  fixed  oils,  or  fats?  67.  What  prop- 
erty do  the  essential  oils  impart  to  foods?  68.  What  food  value  do 
they  possess?  69.  What  dietetic  value  ?  70.  What  are  the  mixed 
compounds?  71.  How  may  a  compound  impart  a  negative  value  to 
a  food?  72.  What  is  the  nutritive  value  of  the  non-nitrogenous 
compounds,  taken  as  a  class?  73.  .Why  is  it  necessary  that 
nitrogenous  and  non-nitrogenous  compounds  be  blended  in  a 
ration?  74.  What  are  the  nitrogenous  compounds?  75.  How  do 
they  differ  from  the  non-nitrogenous  compounds?  76.  Name  the 
four  subdivisions  of  the  nitrogenous  compounds.  77.  What  is 


REVIEW    QUESTIONS  325 

protein?  78.  What  is  characteristic  as  to  its  nitrogen  content? 
79.  What  are  some  of  the  derivative  products  that  can  be  obtained 
from  the  protein  molecule  ?  80.  How  does  the  protein  content  of 
animal  bodies  compare  with  that  of  plants?  81.  Name  the  various 
subdivisions  of  the  proteins.  82.  What  is  albumin,  and  how  may 
it  be  obtained  from  a  food?  83.  What  is  globulin,  and  how  is  it 
obtained  from  a  food?  84.  Give  some  examples  of  globulins. 
85.  What  are  the  albuminates,  and  how  are  they  affected  by  the 
action  of  acids  and  alkalies  ?  86.  What  are  the  peptones,  and  how 
do  they  differ  from  the  albumins?  87.  How  are  the  peptones 
produced  from  other  proteids  ?  88.  What  are  the  insoluble  proteids  ? 
89.  Give  an  example.  90.  Which  of  the  proteids  are  found  to  the 
greatest  extent  in  foods?  91.  Why  may  proteids  from  different 
sources  vary  in  their  nutritive  value ?  92.  What  general  change  do 
the  proteids  undergo  during  digestion?  93.  What  is  crude  protein? 
94.  How  is  the  crude  protein  content  of  a  food  calculated?  95.  Why 
is  the  nitrogen  content  of  a  food  more  absolute  than  the  crude  protein 
content?  96.  What  food  value  do  the  proteins  possess?  97.  Why 
may  proteins  serve  so  many  functions  in  the  body?  98.  Why  is 
protein  necessary  as  a  nutrient  ?  99.  What  is  the  effect  of  an  excess 
of  protein  in  the  ration?  100.  What  is  the  effect  of  a  scant  amount 
of  protein  in  a  ration?  101.  What  are  the  albuminoids?  102.  Name 
some  materials  that  contain  large  amounts  of  albuminoids. 
103.  What  food  value  do  the  albuminoids  possess?  104.  What  are 
the  amids?  105.  How  are  they  formed  in  plants?  106.  What  is 
their  source  in  animals?  107.  What  general  changes  does  the 
element  nitrogen  undergo  in  plant  and  animal  bodies  ?  108.  What 
is  the  food  value  of  the  amids?  109.  What  are  the  alkaloids  ? 
no.  What  is  their  food  value?  in.  What  effect  do  some  alkaloids 
exert  upon  the  animal  body?  112.  How  may  they  be  produced  in 
animal  foods?  113.  What  general  relationship  exists  between  the 
various  nitrogenous  compounds?  114.  Why  is  it  essential  that  the 
animal  body  be  supplied  with  nitrogenous  food  in  the  form  of  pro- 
teids? 115.  Name  the  cycle  of  changes  through  which  the  element 
nitrogen  passes  in  plant  and  animal  bodies. 


326       HUMAN    FOODS   AND   THEIR   NUTRITIVE   VALUE 


CHAPTER    II 


CHANGES  IN  COMPOSITION  OF  FOODS  DURING  COOKING  AND 
PREPARATION 

116.  How  do  raw  and  cooked  foods  compare  in  general  compo- 
sition? 117.  In  what  ways  are  foods  acted  upon  during  cooking? 
118.  What  causes  chemical  changes  to  take  place  during  cook- 
ing? 119.  What  are  the  principal  compounds  that  are  changed 
during  the  process  of  cooking?  120.  How  does  cooking  affect  the 
cellulose  of  foods?  121.  What  change  does  starch  undergo  during 
cooking?  122.  When  foods  containing  starch  are  baked,  what 
change  occurs  ?  123.  How  are  the  sugars  acted  upon  when  foods 
are  cooked?  124.  What  effect  does  dry  heat  have  upon  sugar? 
125.  What  change  occurs  to  the  fats  during  cooking?  126.  How 
does  this  affect  nutritive  value?  127.  What  changes  do  the  pro- 
teids  undergo  during  cooking?  128.  Why  does  the  action  of  heat 
affect  various  proteids  in  different  ways?  129.  Why  are  chemical 
changes,  as  hydration,  often  desirable  in  the  cooking  and  prepara- 
tion of  foods?  130.  What  physical  changes  do  vegetable  and  ani- 
mal tissues  undergo  when  cooked?  131.  How  do  foods  change  in 
weight  during  cooking?  132.  Why  is  a  prolonged  high  temperature 
unnecessary  to  secure  the  best  results  in  cooking?  133.  To  what 
extent  is  the  energy  of  fuels  utilized  for  producing  mechanical  and 
chemical  changes  in  foods  during  cooking?  134.  What  effect  does 
cooking  have  upon  the  bacterial  flora  of  foods?  135.  In  what  ways 
do  bacteria  exert  a  favorable  influence  in  the  preparation  of  foods? 
136.  How  may  certain  classes  of  bacteria  exert  unfavorable  changes 
in  the  preparation  of  foods?  137.  What  are  the  insoluble  fer- 
ments? 138.  What  are  the  soluble  ferments ?  139.  What  part  do 
they  take  in  animal  and  plant  nutrition?  140.  Define  aerobic  fer- 
ments. 141.  Define  anaerobic  ferments.  142.  What  general  rela- 
tionship exists  between  the  chemical,  physical,  and  bacteriological 
changes  that  take  place  in  foods?  143.  Why  should  foods  also 
possess  an  esthetic  value?  144.  What  kinds  of  colors  should  be 


REVIEW    QUESTIONS  327 

used  in  the  preparation  of  foods  ?     145.   What  processes  should  be 
used  for  removal  of  coloring  materials  from  foods  ? 


CHAPTER    III 

VEGETABLE  FOODS 

146.  Give  the  general  composition  of  vegetable  foods  as  a  class. 
147.  How  do  vegetable  foods  differ  from  animal  foods  ?  148.  Name 
some  vegetables  which  contain  the  maximum,  and  some  which 
contain  the  minimum  percentage  of  protein.  149.  Give  the  general 
composition  of  potatoes.  150.  Of  what  is  the  dry  matter  mainly 
composed?  151.  How  much  of  the  crude  protein  of  potatoes  is 
true  protein  ?  152.  What  ratio  exists  between  the  nitrogenous  and 
non-nitrogenous  compounds  in  the  potato  ?  153.  Give  the  chemical 
composition  of  the  potato.  154.  What  influence  do  different 
methods  of  boiling  have  upon  the  crude  protein  content  of  potatoes  ? 
155.  To  what  extent  are  the  nutrients  of  potatoes  digested  and 
absorbed  by  the  body  ?  156.  What  value  do  potatoes  impart  to 
the  ration  ?  157.  How  do  sweet  potatoes  differ  in  chemical  compo- 
sition and  food  value  from  white  potatoes?  158.  How  do  carrots 
differ  in  composition  from  potatoes?  159.  What  is  characteristic 
of  the  dry  matter  of  the  carrot  ?  160.  How  do  carrots  and  milk 
differ  in  composition  ?  161.  To  what  is  the  color  of  the  carrot  due? 
162.  To  what  extent  are  the  nutrients  removed  in  the  cooking  of 
carrots  ?  163.  What  is  the  value  of  carrots  in  a  ration  ?  164.  Give 
the  characteristics  of  the  composition  of  parsnips.  165.  How 
does  the  starch  of  parsnips  differ  from  that  of  potatoes?  166.  How 
does  the  mineral  matter  of  parsnips  differ  from  that  of  potatoes  ? 
167.  How  does  the  cabbage  differ  in  general  composition  from 
many  vegetables  ?  168.  To  what  extent  are  nutrients  extracted 
in  the  boiling  of  cabbage  ?  169.  Give  the  nutritive  value  of 
cabbage.  170.  How  does  the  cauliflower  differ  from  cabbage? 
171.  Give  the  general  composition  of  beets.  172.  Give  the  general 
composition  of  cucumbers.  173.  What  nutritive  value  has  lettuce  ? 


328       HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

174.  Give  the  composition  and  dietetic  value  of  onions.  175.  How 
does  the  ratio  of  nitrogenous  and  non-nitrogenous  compounds  in 
spinach  differ  from  that  in  many  other  vegetables  ?  176.  Give  the 
general  composition  and  nutritive  value  of  asparagus.  177.  How 
much  nutritive  material  do  melons  contain  ?  178.  What  are  the 
principal  compounds  of  tomatoes  ?  179.  What  nutrients  do  they 
supply  to  the  ration?  180.  In  the  canning  of  tomatoes,  why  is  it 
desirable  to  conserve  the  juices  ?  181.  How  does. sweet  corn  dif- 
fer in  composition  from  fully  matured  corn  ?  182.  What  nutritive 
value  does  the  egg  plant  possess  ?  183.  What  are  the  principal 
nutrients  of  squash  ?  184.  What  nutritive  material  does  celery 
contain  ?  185.  To  what  does  celery  owe  its  dietetic  value  ? 
1 86.  Why  are  vegetables  necessary  in  a  ration  ?  187.  Why  is  it  not 
possible  to  value  many  vegetable  foods  simply  on  the  basis  of  per- 
centage of  nutrients  present?  188.  Name  the  miscellaneous  com- 
pounds which  many  vegetables  contain,  and  the  characteristics 
which  these  may  impart.  189.  Why  is  it  necessary  to  consider  the 
sanitary  conditions  of  vegetables  ?  190.  How  do  canned  vegeta- 
bles differ  in  composition  and  food  value  from  fresh  vegetables  ? 
191.  What  proportion  of  vegetables  is  refuse  and  non-edible 
parts  ?  192.  Why  is  it  necessary  to  consider  the  refuse  of  a  food  in 
determining  its  nutritive  value  ? 

CHAPTER  IV 

FRUITS 

193.  To  what  extent  do  fruits  contain  water  and  dry  matter? 
194.  Give  the  general  composition  of  fruits.  195.  What  compounds 
impart  taste  and  flavor?  196.  How  much  nutrients  do  fruits  add  to 
a  ration?  197.  Why  is  it  not  right  to  determine  the  value  of  fruits 
entirely  on  the  basis  of  nutrients  ?  1 98 .  Give  the  general  composition 
of  apples?  199.  What  compound  is  present  to  the  greatest  extent 
in  the  dry  matter  of  apples?  200.  How  do  apples  differ  in  com- 
position? 20 1.  Give  the  general  physical  composition  of  oranges. 


REVIEW    QUESTIONS  329 

202.  What  nutrients  are  present  to  the  greatest  extent  in  oranges? 

203.  How  do  lemons  differ  in  composition  from  oranges?     204.  How 
does  grape  fruit  resemble  and  how  differ  in  chemical  composition 
from  oranges  and  lemons?     205.    What  are  the  main  compounds  in 
strawberries?       206.    In  what  ways  are  strawberries  valuable  in  a 
ration?     207.   Of  what  is  grape  juice  mainly  composed?     208.  What 
acid  is  in  grapes,  and  what  is  its  commercial  value?     209.    To  what 
are  the  differences  in  flavor  and  taste  due?     210.   How  do  ripe  olives 
differ  in  composition  from  green  olives?      211.    What  is  the  food 
value  of  the  olive?     212.    What  physiological  property  does  olive  oil 
have?     213.  What  is  the  principal  nutrient  in  peaches?     214.  What 
compounds  give  flavor  to  peaches?       215.    Of  what  does  the  dry 
matter  of  plums  mainly  consist?     216.    How  do  plums  differ  in  com- 
position from  many  other  fruits?     217.    What  are  prunes?     What  is 
their  food  value?     218.    How  do  dried  fruits  differ  in  composition 
from  fresh  fruits?     219.   What  should  be  the  stage  of  ripeness  of 
fruit  in  order  to  secure  the  best  results  in  canning?     220.    How  do 
canned  fruits  differ  in  composition  and  nutritive  value  from  fresh 
fruits?     221.   To  what  extent  are  metals  dissolved  by  fruit  juices? 
222.    Why  should  tin  in  which  canned  goods  are  preserved  be  of 
good  quality?     223.   What  preservatives  are  sometimes  used  in  the 
preparation  of  canned  fruits?     224.    What  is  the  objection  to  their 
use?     225.    Why  are  fruits  necessary  in  the  ration?       226.    What 
change  does  heat  bring  about  in  the  pectose  substances  of  fruits  ? 

CHAPTER  V 
SUGAR,  MOLASSES,  SIRUPS,  HONEY,  AND  CONFECTIONS 

227.  What  is  sugar?  228.  From  what  sources  are  sugars  ob- 
tained? 229.  Name  the  two  divisions  into  which  sugars  are  divided. 
230.  How  are  sugars  graded  commercially?  231.  What  per  cent 
of  purity  has  granulated  sugar?  232.  How  is  the  coloring  material 
of  sugar  removed?  233.  How  is  sugar  treated  to  make  it  whiter? 
234.  What  value  as  a  nutrient  does  sugar  possess?  235.  Why 


330       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

should  sugar  be  combined  with  other  nutrients  ?  236.  What  foods 
contain  appreciable  amounts  of  sugar?  237.  Why  is  an  excessive 
amount  of  sugar  in  a  ration  undesirable?  238.  Does  sugar  possess 
more  than  condimental  value?  239.  What  is  the  average  quantity 
of  sugar  consumed  in  this  country?  240.  What  is  maple  sugar? 
241 .  How  does  it  differ  in  composition  from  other  sugar?  242.  How 
is  adulterated  maple  sugar  detected?  243.  To  what  extent  is  gran- 
ulated sugar  adulterated?  244.  Why  is  it  not  easily  adulterated? 
245.  What  are  the  dextrose  sugars?  246.  How  do  they  differ 
chemically  from  sucrose?  247.  What  is  the  inversion  of  sugar? 
248.  In  what  way  does  acid  act  upon  sugar?  249.  How  are  the 
acid  products  removed?  250.  What  is  the  food  value  of  glucose? 
251.  What  is  molasses?  252.  How  is  it  obtained?  253.  Of  what 
is  it  composed?  254.  What  gives  taste  and  flavor  to  molasses? 
255.  How  may  molasses  act  upon  metalware?  256.  What  is  the 
food  value  of  molasses?  257.  What  is  sirup?  258.  Name  three 
kinds  of  sirup,  and  mention  materials  from  which  they  are  pre- 
pared. 259.  What  is  the  polariscope,  and  how  is  it  employed  in 
sugar  work?  260.  What  is  honey?  261.  How  does  it  differ  in 
composition  from  sugar?  262.  How  is  strained  honey  adulterated? 

263.  What  materials   are  used  in  the  preparation  of  confections? 

264.  What  changes  take  place  in  their  manufacture?     265.    What 
materials  are  used  for  imparting  color?     266.    What  can  you  say  in 
regard  to  the  coal  tar  colors?    267.    What  should  be  the  position  of 
candy  in  the  dietary?     268.    What  can  you  say  of  the  comparative 
value  of  cane  and  beet  sugar?     269.    How  do  the  commercial  grades 
of  sugar  compare  as  to  nutritive  value?     270.    What  are  some  of 
the  impurities  in  candy?     271.    What  is  saccharine?     272.   What 
are  its  properties  ? 

CHAPTER  VI 

LEGUMES  AND  NUTS 

273.    What   nutrients  do  the   legumes   contain  in  comparatively 
large  amounts  ?     274.    How  does  the  amount  of  this  nutrient  com- 


REVIEW    QUESTIONS  331 

pare  with  that  found  in  meats?  275.  Why  are  legumes  valuable 
crops  in  general  farming  and  for  the  feeding  of  farm  animals? 
276.  Give  the  general  composition  of  beans.  277.  How  do  beans 
compare  in  protein  content  with  cereals  ?  278.  How  does  the  protein 
of  beans  differ  from  that  of  many  other  food  materials  ?  279.  To  what 
extent  are  the  nutrients  of  beans  digested?  280.  What  influence 
does  the  combination  of  beans  with  other  foods  have  upon  digesti- 
bility? 281.  What  influence  does  removal  of  skins  have  upon 
digestibility?  282.  In  what  part  of  the  digestive  tract  are  beans 
mainly  digested?  283.  How  does  the  cost  of  the  nutrients  in  beans 
compare  with  that  of  the  nutrients  in  other  foods  ?  284.  How  do 
string  beans  differ  from  green  beans?  285.  Give  the  general  com- 
position, digestibility,  and  nutritive  value  of  peas.  286.  What 
can  you  say  of  the  use  of  copper  sulphate  in  the  preparation  of 
canned  peas?  287.  What  nutrients  do  peanuts  contain  in  large 
amounts?  288.  Give  the  general  composition  of  nuts.  289.  What 
are  the  characteristics  of  pistachio?  290.  Give  the  general  com- 
position of  the  cocoanut.  291.  What  is  cocoanut  butter?  292.  To 
what  extent  may  nuts  contribute  to  the  nutritive  value  of  a  ra- 
tion ? 


CHAPTER  VII 
MILK  AND  DAIRY  PRODUCTS 

293.  What  can  you  say  as  to  the  importance  of  dairy  products  in 
the  dietary?  294.  Give  the  general  composition  of  milk.  295.  What 
compound  in  milk  is  most  variable?  296.  To  what  extent  are 
the  nutrients  in  milk  digestible?  297.  What  influence  does  milk 
have  upon  the  digestibility  of  other  foods?  298.  Why  is  cheese 
cured  in  cold  storage?  299.  How  can  the  tendency  of  a  milk  diet 
to  produce  costiveness  be  overcome?  300.  Why  is  it  necessary  to 
consider  the  sanitary  condition  of  milk?  301.  What  factors  in- 
fluence the  sanitary  condition  of  milk?  302.  What  is  certified  milk ? 
303.  What  is  pasteurized  milk?  304.  How  can  milk  be  pasteurized 


332       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

for  family  use?  305.  What  is  tyrotoxicon  ?  306.  What  is  its 
source  in  milk?  307.  To  what  is  the  color  of  milk  due?  308.  To 
what  extent  is  color  associated  with  fat  content  ?  309.  What 
causes  souring  of  milk?  310.  What  change  occurs  in  the  milk 
sugar?  311.  What  are  the  most  favorable  conditions  for  the  sour- 
ing of  milk?  312.  What  are  some  of  the  preservatives  used  in  milk. 
313.  What  objection  is  urged  against  their  use?  314.  What  is  con- 
densed milk?  315.  What  is  buttermilk,  and  what  dietetic  value  has 
it?  316.  How  does  goats1  milk  differ  from  cows1  milk?  317.  What 
is  koumiss,  and  how  is  it  prepared?  318.  What  are  the  pre- 
pared milks?  319.  How  does  human  milk  differ  in  composition 
from  cows1  milk?  320.  Give  the  nutritive  value  of  skim  milk. 
321.  What  content  of  fat  should  cream  contain?  322.  In  what 
ways  is  milk  adulterated  ?  323.  How  are  these  adulterations  de- 
tected ?  324.  Give  the  general  composition  of  butter.  325.  What 
is  the  maximum  amount  of  water  that  a  butter  may  contain  without 
being  considered  adulterated  ?  326.  What  can  you  say  in  regard 
to  the  digestibility  of  butter  ?  327.  How  is  butter  adulterated  ? 
328.  How  does  oleomargarine  compare  in  digestibility  and  food  value 
with  butter  ?  329.  What  is  the  food  value  of  butter  ?  330.  How 
does  cheese  differ  in  composition  from  butter?  331.  Give  the 
general  composition  of  cheese.  332.  To  what  are  the  flavor  and 
odor  of  cheese  due  ?  333.  Why  is  cheese  ripened  ?  334.  What 
chemical  changes  take  place  during  ripening  ?  335.  To  what  extent 
are  the  nutrients  of  cheese  digested  ?  336.  Why  is  cheese  some- 
times considered  indigestible?  337.  To  what  extent  do  the  nu- 
trients of  different  kinds  of  cheese  vary  in  digestibility  ?  338.  How 
does  cheese  compare  in  nutritive  value  and  cost  with  meats  ? 
339.  What  is  cottage  cheese  ?  340.  What  is  Roquefort  cheese  ? 
341.  Name  four  kinds  of  cheese,  and  say  to  what  each  owes 
its  individuality.  342.  How  is  cheese  adulterated  ?  343.  Why 
are  dairy  products  in  older  agricultural  regions  generally  cheaper 
than  meats  ? 


REVIEW    QUESTIONS  333 


CHAPTER  VIII 
MEATS  AND  ANIMAL  FOOD  PRODUCTS 

344.  Give  the  general  composition  of  meats.  345.  How  do  meats 
differ  in  chemical  composition  from  vegetable  foods  ?  346.  What 
is  the  principal  non-nitrogenous  compound  of  meats,  and  what 
of  vegetables  ?  347.  Name  the  different  classes  of  proteins  in 
meats.  348.  Which  class  is  present  in  largest  amounts  ?  349.  To 
what  extent  are  amid  compounds  present  in  meats  ?  350.  What 
characteristics  do  amids  impart  to  meats  ?  351.  How  are  alkaloids 
produced  in  meats  ?  352.  In  what  ways  does  the  lean  meat  of 
different  kinds  of  animals  vary  chemically  and  physically  ?  353.  Give 
the  general  composition  of  beef.  354.  What  relationship  ex- 
ists between  the  fat  and  water  content  of  beef?  355.  How  much 
refuse  have  meats  ?  356.  In  what  forms  are  the  ash  elements 
(mineral  matter)  present  in  meats  ?  357.  How  does  veal  differ  in 
composition  from  beef  ?  358.  What  general  changes  in  composi- 
tion occur  as  animals  mature?  359.  How  do  these  compare  with 
the  changes  that  take  place  when  plants  ripen  and  seeds  are  pro- 
duced ?  360.  How  does  mutton  vary  in  composition  from  beef  ? 
361.  How  does  it  compare  in  food  value  with  beef  ?  362.  How  do 
lamb  and  mutton  differ  in  composition  ?  363.  To  what  extent  do 
the  various  cuts  differ  in  composition  ?  364.  How  do  the  more  ex- 
pensive cuts  of  lamb  compare  in  nutritive  value  with  the  less 
expensive  cuts  ?  365.  How  does  pork  differ  in  composition  from 
other  .  meats  ?  366.  Give  the  general  composition  of  ham. 
367.  Give  the  composition  and  nutritive  value  of  bacon.  368.  How 
does  bacon  compare  in  food  value  with  other  meats  ?  369.  How 
does  the  character  of  the  fat  influence  the  composition  and  taste  of 
the  meat  ?  370.  What  influences  the  texture  or  toughness  of 
meats  ?  371.  How  do  cooked  meats  compare  in  composition  with 
raw  meats  ?  372.  To  what  extent  are  nutrients  lost  in  the  boiling 
of  meats  ?  373.  What  influence  does  the  temperature  of  the  water 


334       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 

in  which  the  meat  is  placed  for  cooking  have  upon  the  amount  of 
nutrients  extracted  ?  374.  To  what  is  the  shrinking  of  meats  in 
cooking  due  ?  375.  Of  what  does  meat  extract  mainly  consist  ? 
376.  To  what  do  beef  extracts  owe  their  flavor  ?  377. 
their  food  value  ?  378.  What  is  their  dietetic  value  ?  3;  /v'hat 
is  lard  ?  380.  How  does  it  differ  in  composition  from  other  fats  ? 

381.  What  is    imparted   to   meats   during   the   smoking  process  ? 

382.  Why  is  saltpeter  used  in  the  preservation  of  meats  ?     383.    Do 
vegetable   foods   contain   nitrates   and  nitrites  ?      384.    How   does 
poultry  resemble  and  how  differ  in  composition  from  other  meat  ? 
385.   Give  the  characteristics  of  sound  poultry.         386.    Give  the 
general  composition  of  fish.     387.    How  does  the  flesh  of  different 
kinds  of  fish  vary  in  composition?     388.    What  influence  does  salt- 
ing and  preservation  have  upon  composition  ?     389.    How  do  fish 
and   meat   compare  in  digestibility?     390.    How  does  the  mineral 
matter  and  phosphate  content  of  fish  compare  with  that  of  other 
foods  ?     391.   What  are  the  main  nutrients  in  oysters?     392.    Give 
the  general  food  value  of  oysters.     393.  What  is  meant  by  the  fatten- 
ing of  oysters  ?     394.  What  effect  does  the  character  of  the  water  used 
in  fattening  have  upon  the  sanitary  value  ?     395.    Give  the  general 
composition  of  the  egg.     396.    How  do  different  parts  of  the  egg 
differ  in  composition  ?     397.    How  does  the  egg  differ  in  composi- 
tion from  the  potato  ?     398.    Is  color  an  index  to  the  composition 
of  the  egg  ?     399.   What  effect  does  cooking  have  upon  the  compo- 
sition of  the  egg?    400.   What  factors  influence  the  flavor  of  eggs  ? 

401.  How   do  different  ways   of  cooking   affect   the   digestibility? 

402.  Under  what  conditions  can  eggs  be  used  economically  in  the 
dietary?     403.    Why  should  eggs  be  purchased  and  sold  by  weight? 

404.  How  do  canned  meats  differ  in  composition  from  fresh  meats  ? 

405.  How  do  the  nutrients  of  canned  meats  compare  in  cost  with 
those   of  fresh  meat?    406.    What  are  the  advantages  of  canned 
meats  over  fresh  meats?    407.    What  are  some  of  the  materials  used 
in  the  preservation  of  meats  ? 


REVIEW   QUESTIONS  335 

CHAPTER  IX 

CEREALS 

408.  'How  are  the  cereals  milled?  409.  What  are  the  cereals 
most  commonly  used  for  food  purposes?  410.  Give  the  general 
composition  of  cereals  as  a  class.  411.  What  are  the  main  nutri- 
ents in  corn  preparations?  412.  What  influence  does  the  more 
complete  removal  of  the  bran  and  germ  of  corn  have  upon  its  diges- 
tibility? 413.  How  does  the  cost  of  nutrients  in  corn  compare 
with  other  foods?  414.  Why  is  corn  alone  not  suitable  for  bread- 
making  purposes?  415.  Why  should  corn  be  combined  in  a  ration 
with  foods  mediumly  rich  in  protein?  416.  What  change  takes 
place  in  corn  meal  from  long  storage?  417.  Give  the  characteris- 
tics and  composition  of  oat  preparations.  418.  How  does  removal 
of  the  oat  hull  affect  the  composition  of  the  product?  419.  To 
what  extent  do  the  various  oat  preparations  on  the  market  differ  in 
composition  and  food  value?  420.  Do  oats  contain  any  special 
alkaloidal  or  stimulating  principle?  421.  Why  should  oatmeal 
receive  longer  and  more  thorough  cooking  than  many  other 
foods?  422.  To  what  extent  are  the  nutrients  in  oatmeal  digested? 
423.  How  do  wheat  preparations  differ  in  general  composition 
from  corn  and  oat  preparations?  424.  What  influence  upon  the 
composition  of  the  wheat  breakfast  foods  has  partial  or  complete 
removal  of  the  bran  ?  425.  What  is  the  effect  upon  their  digesti- 
bility and  nutritive  value?  426.  What  are  the  special  diabetic 
flours,  and  how  are  they  prepared?  427.  What  are  the  wheat  mid- 
dlings breakfast  foods,  and  how  do  they  compare  in  digestibility  and 
food  value  with  bread?  428.  How  do  they  differ  mechanically? 

429.  How  does  barley  differ  from  wheat  in  general    composition? 

430.  What  is  barley  water,  and   what   nutritive   material   does   it 
contain?     431.    What  cereal   does  rice  resemble   in   composition? 
432.    With  what  food  materials  should  rice  be  combined  to  make 
a  balanced  ration?     433.    What  can  you  say  as  to  comparative  ease 


336       HUMAN    FOODS    AND    THEIR   NUTRITIVE    VALUE 

and  completeness  of  digestibility  of  rice?  434.  Why  are  cereals 
valuable  in  the  ration?  435.  In  what  way  do  they  take  a  me- 
chanical part  in  digestion?  436.  What  are  predigested  breakfast 
foods  ?  437.  How  would  you  determine  the  general  nutritive  value 
of  a  breakfast  food,  knowing  the  kind  of  cereal  from  which  it  was 
prepared?  438.  To  what  extent  are  cereals  modified  or  changed  in 
composition  by  cooking?  439.  To  what  extent  are  the  nutrients  of 
cereal  foods  digested  and  absorbed  by  the  body  ?  440.  To  what  ex- 
tent do  the  cereals  supply  the  body  with  mineral  matter?  441.  How 
does  the  phosphate  content  of  cereals  compare  with  that  of  meats 
and  milk? 


CHAPTER  X 

WHEAT  FLOUR 

442.  Why  is  wheat  flour  especially  adapted  to  bread-making  pur- 
poses? 443.  To  what  extent  may  wheat  vary  in  protein  content? 
444.  What  are  spring  wheats  ?  445.  What  are  winter  wheats  ? 
446.  Give  the  general  characteristics  of  each.  447.  What  are  gluti- 
nous wheats?  448.  What  are  starchy  wheats?  449.  Name  the 
different  proteids  in  wheat  flour.  450.  About  how  much  starch  does 
wheat  flour  contain  ?  451.  What  other  carbohydrates  are  also  pres- 
ent? 452.  What  is  the  roller  process  of  flour  milling?  453.  What 
is  meant  by  the  first  break  ?  454.  How  are  the  different  products  of 
the  wheat  kernel  separated?  455.  What  is  meant  by  middlings 
flour?  456.  What  is  break  flour?  457.  What  is  patent  flour? 
458.  Name  the  high  grade  flours.  459.  Name  the  low  grade  flours. 
460.  How  are  the  impurities  removed  from  wheat  flour?  461.  What 
per  cent  of  the  wheat  kernel  is  returned  as  flour?  As  offals  ? 
462.  What  becomes  of  the  wheat  germ  during  milling?  463.  What 
sized  bolting  cloths  are  used  in  milling?  464.  What  is  graham 
flour?  465.  How  does  it  differ  in  mechanical  and  chemical  com- 
position from  white  flour?  466.  What  is  entire  wheat  flour? 
467.  How  does  it  differ  in  physical  and  chemical  composition  from 


REVIEW    QUESTIONS  337 

white  flour?  468.  What  effect  has  the  refining  of  flour  upon  the  ash 
content?  469.  How  do  low  and  high  grade  flours  differ  in  chemical 
composition?  470.  How  do  the  wheat  offals  differ  in  composition 
from  the  flour?  471.  What  are  the  factors  which  influence  the  com- 
position of  flours  ?  472.  What  effect  does  storage  have  upon  the 
bread-making  value  of  flour  ?  473.  What  change  takes  place  when 
new  wheat  is  stored  in  an  elevator?  474.  What  is  durum  wheat  flour, 
and  how  does  it  differ  from  other  flour?  475.  What  gives  flour  its 
color?  476.  Why  is  color  an  index  of  grade?  477.  How  is  the 
color  of  a  flour  determined  ?  478.  How  do  flours  differ  in  granula- 
tion? 479.  How  does  the  granulation  affect  the  physical  properties 
of  flour?  480.  How  is  the  granulation  of  flour  approximately  deter- 
mined? 481.  How  is  the  absorptive  capacity  of  a  flour  determined  ? 
482.  What  factors  cause  a  variation  in  the  capacity  of  flours  to 
absorb  water?  483.  Give  the  characteristics  of  a  good  gluten. 
484.  What  causes  unsound  flours?  485.  How  is  the  bread-making 
value  of  a  flour  determined  ?  486.  How  are  flours  bleached  ? 
487.  How  does  bleaching  affect  the  chemical  composition  of 
flour  ?  488.  What  influence  does  bleaching  have  upon  bread- 
making  value?  489.  Traces  of  what  compounds  are  formed  during 
bleaching  ?  490.  Are  these  compounds  injurious  to  health  ? 
491.  What  effect  does  bleaching  have  upon  the  color  of  fiber  and 
debris  particles  in  flour?  492.  Is  it  possible  to  bleach  low  grade 
flours  and  cause  them  to  resemble  high  grade  flours?  493.  Are 
flours  usually  adulterated  ?  494.  Why  ?  495.  How  would  mineral 
adulterants  be  detected  ?  496.  How  would  the  presence  of  other 
cereals  be  detected  ?  497.  How  does  flour  compare  in  nutritive 
value  with  other  foods?  498.  How  does  the  cost  of  flour  compare 
with  that  of  other  foods  ?  499.  What  causes  flours  to  vary  so  in 
bread-making  value  ?  500.  Why  may  flours  produced  from  the 
same  type  of  wheat  vary  slightly  in  character  from  year  to  year  ? 
501.  What  relationship  exists  between  the  nutritive  and  bread- 
making  value  of  a  flour? 


338       HUMAN    FOODS    AND   THEIR    NUTRITIVE    VALUE 


CHAPTER  XI 
BREAD  AND  BREAD  MAKING 

502.  Define  leavened  and  unleavened  bread.  503.  Why  is  yeast 
used  in  bread  making  ?  504.  Give  the  characteristics  of  a  good  loaf 
of  bread.  505.  Why  is  flour  used  for  bread  making  purposes? 
506.  Name  the  eight  chemical  changes  that  take  place  during  bread 
making.  507.  To  what  extent  do  losses  in  dry  matter  occur  during 
bread  making  ?  508.  What  compounds  suffer  losses  during  bread 
making  ?  509.  What  is  yeast  ?  510.  What  chemical  changes  does 
it  produce  ?  511.  What  becomes  of  these  products  during  bread 
making  ?  512.  How  is  compressed  yeast  made  ?  513.  What  part 
does  the  alcohol  take  in  bread  making?  514.  What  temperature 
is  reached  in  the  interior  of  the  loaf  during  bread  making  ? 
515.  Through  what  chemical  changes  does  starch  pass  during 
bread  making?  516.  To  what  extent  are  soluble  carbohydrates 
formed?  517.  In  what  way  is  starch  acted  upon  mechanically? 

518.  Explain   the  structure   of  the   starch  grains  in  flour  and  in 
dough  after  they   have   been   acted   upon   by  the   yeast  ferments. 

519.  To    what  ,  extent    are    acids   produced  in    bread    making? 

520.  What  becomes  of  the  acids  formed  ?     521.    How  may  the  acids 
thus  developed  affect  the  properties  of  other  chemical  compounds  ? 

522.  To  what  extent  are  volatile  carbon  compounds,  other  than 
carbon    dioxid    and    alcohol,    liberated     during     bread     making  ? 

523.  What  changes  occur  to  the  various  proteids  during  the  process 
of  bread  making  ?     524.   Why  do  flours  vary  in  quality  of  gluten  ? 
525.   To  what   extent  do   losses    of  nitrogen   occur   during   bread 
making?     526.    How  much  of  the  total  nitrogen  of  flour  is  present  as 
proteids  ?     527.    How  is  the  fat  of  flour  affected  during  the  process  of 
bread  making?    528.   What  effect  does  the  addition  of  10  per  cent  of 
wheat  starch  to  flour  have  upon  the  size  of  the  loaf  ?    529.  What  effect 
does  the  addition  of  10  per  cent  of  wheat  gluten  to  flour  have  upon  the 
size  of  the  loaf  ?     530.  What  relationship  exists  between  gluten  con- 
tent and  capacity  of  a  flour  to  absorb  water?     531.    Give  the  general 


REVIEW    QUESTIONS  339 

composition  of  bread.  532.  What  factors  influence  its  composition? 
533.  What  effect  does  the  use  of  skim  milk  and  lard  in  bread 
making  have  upon  composition?  534.  How  does  the  temperature 
of  the  flour  influence  the  bread-making  process?  535.  Why  is  it 
necessary  to  vary  the  process  of  bread  making  in  order  to  get  the 
best  results  with  different  kinds  of  flour?  536.  To  what  extent  are 
the  nutrients  of  bread  digested?  537.  How  does  graham  bread 
compare  in  digestibility  with  white  bread?  538.  How  do  graham 
and  entire  wheat  breads  compare  in  nutritive  value  with  white  bread? 
539.  What  value  do  graham  and  entire  wheat  breads  have  in  the 
dietary?  540.  Why  is  white  bread  generally  preferable  in  the 
dietary  of  the  laboring  man?  541.  How  do  graham  and  entire 
wheat  flours  compare  in  chemical  composition  with  white  flour? 
542.  How  do  they  compare  in  mechanical  composition?  543.  To 
what  is  the  difference  in  digestibility  supposed  to  be  due?  544.  Are 
graham  and  entire  wheat  breads  necessary  in  a  ration  as  a  source  of 
mineral  elements?  545.  What  is  the  main  difference  in  composition 
between  old  and  new  bread?  546.  How  do  different  kinds  of  bread 
made  from  the  same  flour  compare  in  composition  and  nutritive 
value?  447.  How  does  toast  differ  in  composition  from  bread? 

548.  What    influence     does     toasting     have     upon     digestibility? 

549.  What   is   gained  by  toasting   bread?     550.    How  does  bread 
compare  in  nutritive  value  with  other  cereal  foods?     551.    How  does 
bread  compare  in  nutritive  value  with  animal  foods? 


CHAPTER  XII 
BAKING  POWDERS 

552.  What  is  a  baking  powder?  553.  What  are  the  two  kinds 
of  materials  which  baking  powders  contain?  554.  Name  the  differ- 
ent types  of  baking  powders.  555.  How  does  baking  powder  differ 
in  its  action  from  yeast?  556.  What  are  the  cream  of  tartar  baking 
powders?  557.  What  is  the  nature  of  the  residue  which  they  leave? 
558.  What  are  the  phosphate  baking  powders?  559.  What  is  the 


340        HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

nature  of  the  residue  which  they  leave?  560.  Why  is  the  mineral 
phosphate  not  considered  equally  valuable  with  that  naturally  present 
in  foods?  561.  What  are  the  alum  baking  powders?  562.  What 
residue  is  left  from  the  alum  powders?  563.  Which  of  the  three 
classes  of  baking  powders  is  considered  the  least  objectionable? 
564.  Why  is  a  new  baking  powder  preferable  to  one  that  has  been 
kept  a  long  time?  565.  Why  should  baking  powders  be  kept  in  tin 
cans,  and  not  in  paper?  566.  Why  are  fillers  used  in  the  manufac- 
ture of  baking  powders?  567.  How  may  a  baking  powder  be  pre- 
pared at  home?  568.  How  does  such  a  baking  powder  compare  in 
cost  and  efficiency  with  those  purchased  in  the  market  ? 


CHAPTER  XIII 
VINEGARS,  SPICES,  AND  CONDIMENTS 

569.  What  is  vinegar?  570.  How  is  it  made?  571.  Give  the 
three  chemical  changes  that  take  place  in  its  preparation.  572.  Why 
is  air  necessary  in  the  last  stage  of  the  process  ?  573.  What  ferments 
take  part  in  the  production  of  vinegar  ?  574.  What  is  malt  vinegar? 
575.  What  materials  other  than  apples  can  be  used  in  the  prepa- 
ration of  vinegar?  576.  Give  the  characteristics  of  a  good  vinegar. 
577.  In  what  ways  are  vinegars  adulterated?  578.  What  food  value 
has  vinegar?  579.  Why  should  vinegars  not  be  stored  in  metalware ? 
580.  What  dietetic  value  has  vinegar?  581.  To  what  materials  do 
the  spices  owe  their  value?  582.  What  is  pepper?  583,  What  is 
the  difference  between  white  and  black  pepper?  584.  What  com- 
pounds give  pepper  its  characteristics?  585.  How  are  peppers  adul- 
terated? 586.  What  is  mustard  ?  587.  Give  its  general  composition. 
588.  How  is  it  adulterated?  589.  What  is  ginger?  590.  How  is 
it  prepared  for  the  market?  591.  Give  its  general  composition. 
592.  What  is  cinnamon?  593.  What  is  cassia?  594.  What  gives 
these  their  taste  and  flavor  ?  595.  What  are  cloves  ?  596.  How  are 
they  prepared?  597.  What  is  mace?  598.  What  is  nutmeg? 


REVIEW   QUESTIONS  341 

r 

599.  Do  the  spices  have  any  food  value?  600.  What  is  their  dietetic 
value?  601.  Why  is  excessive  use  of  some  of  the  spices  objection- 
able? 


CHAPTER  XIV 
TEA,  COFFEE,  CHOCOLATE,  AND  COCOA 

602.  What  is  tea?  Name  the  two  plants  from  which  it  is  ob- 
tained, the  countries  where  each  grows  best,  and  the  number  of 
flushes  each  yields.  603.  Upon  what  does  the  quality  and  grade  of 
tea  depend?  604.  Give  differences  in  the  preparation  and  composi- 
tion of  green  and  black  teas.  605.  The  characteristic  flavor  of  tea 
is  imparted  by  what  compound?  606.  To  what  compound  are  its 
peculiar  physiological  properties  due?  607.  What  can  you  say  of 
the  protein  in  tea  as  to  amount  and  food  value?  608.  Why  should 
tea  —  especially  green  tea — be  infused  for  a  very  short  time,  never 
boiled  ?  609.  What  effect  has  tannin  upon  the  digestion  of  proteids  ? 
610.  What  three  points  are  considered  in  judging  a  tea?  61 1 .  What 
is  the  most  common  form  of  tea  adulteration?  612.  Describe  the 
coffee  plant  and  fruit,  and  its  method  of  preparation  for  market. 
613.  What  is  the  difference  in  the  chemical  composition  of  tea 
and  coffee?  614.  Name  the  characteristic  alkaloid  of  coffee. 
How  does  it  compare  with  theine?  615.  Why  may  coffee  not  be 
considered  a  food?  616.  Tell  different  ways  in  which  coffee  may  be 
adulterated.  617.  Which  is  more  commonly  practiced,  tea  or  coffee 
adulteration?  Why?  618.  How  may  real  coffee  be  distinguished 
from  chicory?  Why?  619.  Name  the  three  kinds  of  coffee  in 
general  use.  Give  distinguishing  features  of  each.  Which  is  usu- 
ally considered  best?  620.  From,  what  are  cocoa  and  chocolate 
obtained?  621.  Give  the  two  methods  of  preparing  cocoa. 
622.  What  alkaloid  similar  to  the  theine  and  caffeine  of  tea  and 
coffee  is  present  in  cocoa  and  chocolate  ?  623.  What  is  the  difference 
in  preparation  of  cocoa  and  chocolate  ?  624.  What  are  cereal  coffee- 
substitutes?  625.  What  nutritive  value  have  they  ?  626.  How  do 


342       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

they  differ  in  composition  from  coffee?  627.  To  what  extent  does 
cocoa  add  to  the  nutritive  value  of  a  ration?  628.  What  is  plain 
chocolate?  629.  Why  do  chocolate  preparations  vary  so  widely 
in  composition?  630.  What  treatment  is  given  to  the  cocoa  bean 
in  its  preparation  for  commerce?  631.  What  treatment  is  some- 
times given  to  prevent  separation  of  the  cocoa  fat?  632.  In 
what  ways  may  cocoa  and  chocolate  preparations  be  adulter- 
ated? 


CHAPTER  XV 

DIGESTIBILITY  OF  FOODS 

633.  Define  the  term  nutrient.  634.  Do  all  the  nutrients  of 
food  have  the  same  degree  of  digestibility?  635.  What  is  a  diges- 
tion coefficient?  636.  How  is  the  digestibility  of  a  food  deter- 
mined? 637.  What  volatile  products  are  formed  during  the  diges- 
tion of  food?  638.  Define  digestible  protein;  digestible  carbohy- 
drates, digestible  fat.  639.  What  is  the  available  energy  of  a  ration  ? 
640.  How  is  it  determined?  641.  How  do  the  nutrients,  pro- 
tein, fat,  and  carbohybrates,  compare  as  to  available  energy? 

642.  Why  is  it  necessary  to  consider  the  caloric  value  of  a  ration? 

643.  Is  the  protein  molecule  as  completely  oxidized  in    the  body 
as  starch  or  fat?     644.    What  residue  is  left  from  the  digestion  of 
protein?     645.    What  part  do  the  soluble  ferments  take  in  diges- 
tion?    646.    To  what  extent  are  the  nutrients  of  animal  foods  di- 
gested?    647.    Which  nutrient,  protein  or  fat,  is  the  most  completely 
digested?     648.    How  do  vegetable  foods  compare  in  digestibility 
with   animal   foods?     649.    What   effect  does    cellulose  have  upon 
digestibility?     650.    Which  of  the  nutrients  of  vegetables,  protein  or 
carbohydrates,  is  more  completely  digested?     651.   What  mechani- 
cal value  may  cellulose  have  in  a  ration?     652.    Why  must  bulk  be 
considered   in  a  ration,  as  well  as  nutrient   content  £     653.    Name 
the  eight  most  important  factors   influencing   the   digestibility  of 
foods.     654.    To  what  extent  does  the  combination  of  foods  affect 


REVIEW    QUESTIONS  343 

the  digestibility  of  the  nutrients?  655.  Why  does  a  mixed  ration 
give  better  results  than  when  only  a  single  food  is  used?  656.  How 
does  the  amount  consumed  affect  the  completeness  of  the  digestive 
process?  657.  To  what  extent  does  the  method  of  preparing  food 
affect  digestibility?  658.  What  is  gained,  so  far  as  digestibility  is 
concerned,  by  the  cooking  of  foods?  659.  To  what  extent  does 
the  mechanical  condition  of  food  affect  its  digestibility?  660.  Why 
is  it  desirable  to  have  some  coarsely  granulated  foods  in  a  ration  ? 
661.  Why  should  the  ration  not  be  composed  exclusively  of  finely 
granulated  foods  ?  662.  Why  is  some  coarsely  granulated  food 
more  essential  in  the  dietary  of  the  sedentary  than  in  the  dietary 
of  the  laborer  ?  663.  How  does  palatability  affect  the  digestive 
process  ?  664.  Do  psychological  processes  in  any  way  affect 
digestion?  665.  What  physiological  properties  do  some  foods 
possess  ?  666.  To  what  are  these  physiological  properties  due  ? 

667.  To    what    extent    is    individuality    a   factor    in    digestion  ? 

668.  To   what   extent  does   digestibility    differ   with    individuals? 

669.  Why    do    some    foods    affect  individuals  in    different    ways  ? 

670.  Why  is  it  necessary  that  the  quantity,  quality,  and  character 
of  the  food  should  vary  with  different  individuals?     67^1.    In  what 
different    ways  is  the  expression  "digestibility  of  a  food"  used? 
672.   Why  is  it  necessary  to  consider  the  digestibility  of  food,  as 
well  as  its  composition  ?     673.    Does  the  digestibility  of  a  food  nec- 
essarily indicate  the  economic  uses  that  will  be  made  of  it  by  the 
body?     674.    How  is  it  possible  for  one  food  containing  10  per 
cent  of  digestible  protein,  and  other  nutrients  in  like  amounts,  to  be 
more  valuable  than  another  food  with  the  same  per  cent  of  digesti- 
ble protein  and  other  nutrients?     675.    How  is  it  possible  for  one 
food  to  contain  less  total  protein  than  another  food  and  yet  be  more 
valuable  from  a  nutritive  point  of  view  ?     676.    Why  is  it  necessary 
to  consider  the  mechanical  condition  of  a  food  and  its  combination 
with  othe"r  foods,  as  well  as  its  chemical  composition  ?     677.    What 
effect  does  lack  of  a  good  supply  of  air  have  upon  the  completeness 
of  the  digestion  process  ?     678.    In  what  ways  does  the  digestion  of 
food  resemble  the  combustion  of  fuel  ?     679.    What  is  gained  by  a 


344       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

study  of  the  digestibility  of  foods  ?  680.  Why  may  two  foods  of 
the  same  general  character  give  different  results  when  used  for  nu- 
tritive purposes? 

CHAPTER  XVI 

COMPARATIVE  COST  AND  VALUE  OF  FOODS 

68  r.  To  what  extent  do  the  nutritive  value  and  the  market  price 
of  foods  vary  ?  682.  How  is  the  value  of  one  food  expressed  in 
terms  of  another  food  ?  683.  How  determine  the  amount  of  nutri- 
ents that  can  be  procured  in  a  food  for  a  given  sum  of  money  ? 
684.  How  compare  the  amounts  of  nutrients  that  can  be  procured 
in  two  foods  for  a  given  sum  of  money  ?  685.  How  is  it  possible 
to  determine  approximately  which  of  two  foods  is  cheaper,  when  the 
price  and  composition  of  the  foods  are  known  ?  686.  To  what 
nutrient  is  preference  usually  given  in  assigning  a  value  to  a  food  ? 
687.  When  the  difference  in  this  nutrient  between  two  foods  is 
small,  then  the  preference  is  given  to  what  nutrients  ?  688.  At 
ordinary  prices,  what  are  the  cheapest  vegetable  foods  ?  689.  What 
are  among  the  cheapest  animal  foods  ?  690.  Why  is  it  not  possible 
to  determine  the  value  of  a  food  absolutely  from  its  composition  and 
digestibility  ?  691.  Why  is  it  necessary  to  consider  the  physical 
as  well  as  the  chemical  composition  of  foods  ?  692.  What  propor- 
tion of  the  income  of  the  laboring  man  is  usually  expended  for 
food  ?  693.  What  are  the  most  expensive  foods  ?  .694.  What 
foods  furnish  the  largest  amount  of  nutrients  at  the  least  cost  ? 


CHAPTER  XVII 

DIETARY  STUDIES 

695.  What  is  a  dietary  study?  696.  How  is  a  dietary  study 
made  ?  697.  What  is  the  value  of  the  dietary  study  of  a  family  ? 
698.  To  what  extent  does  the  protein  in  the  dietary  range  ? 


REVIEW    QUESTIONS  345 

699.  Why  is  a  scant  amount  of  protein  in  a  ration   undesirable  ? 

700.  Why    is   an    excess   of   protein  in  the   ration    undesirable  ? 

701.  What  are  dietary  standards  ?     702.    How  are  such  standards 
obtained  ?     703.    Why  is  it  desirable  in  a  ration  to  secure  the  pro- 
tein and  other  nutrients  from  a  variety  rather  than  from  a  few  foods  ? 

704.  Why  is  it  necessary  to  consider  the  caloric  value  of  a  ration  ? 

705.  How   is    this    determined  ?     706.    What  is  a    wide    nutritive 
ratio?      707.    What  is  a  narrow  nutritive  ratio?     708.  .Why  should 
the  amount  of  nutrients  consumed  vary  with  the  work  performed? 

709.  How  should  the  nutrients  be  apportioned  among  the  meals? 

710.  What    are     some     of   the    most     common     dietary    errors? 

711.  What  analogy   exists   between   human  and  animal  feeding? 

712.  What  is  gained  by  the  rational  feeding  of  both  humans  and 
animals?     713.    What  use  can   be  made   of   the  results  of  dietary 
studies  for  improvement  of  the  dietary?      714.    Why  is  it  not  pos- 
sible for  animal  foods  to  compete  in  economy  with  cereal  and  vege- 
table foods?      715.    Is  a  well-balanced  ration   and  one  containing 
an  ample  supply   of   nutrients    necessarily   an    expensive    ration? 
716.    Show  how  it  is  possible  for  one  family  to  spend  less  money 
for  food  than  another  family,  and  yet  secure  more  digestible  nutrients 
and  energy.     717.    What  are  some  of  the  most  erroneous  ideas  as  to 
food  values?      718.   Why  is    it    necessary  to    consider   previously 
acquired  food  habits  in  the  selection  of  foods?     719.    In  general, 
what  portion  of  the  nutrients  of  a  ration  should  be  derived  from 
vegetable  foods,  and  what  portion  from    meats?      720.    To  what 
extent  may  a  ration  vary  from  the  dietary  standards?      721.    Why 
are  some  inexpensive  foods  often  expensive  when  prepared  for  the 
table?    722.    What  are  some  of  the  ways  in  which  the  cost  of  a  ration 
can  be  decreased  without  sacrificing  nutritive  value?     723.    Why  do 
different  nationalities  acquire  distinct  food  habits  ?      724.    Why  is 
it  not  possible  to  make  sudden  and  radical  changes  in  the  dietary  ? 
725.   Why  is  it  not  possible  fora  dietary  which  gives  ample  satis- 
faction for  one  class  of  people  to  be  applied  to  another  class  with 
equal  satisfaction?     726.   What  relationship  exists  between  the  die- 
tary of  a  nation  and  its  physical  development?     727.    What  rela- 


346       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

tionship  exists  between  dietary  habits  and  mental  development  and 
vigor?  728.  Why  is  it  unnecessary  and  undesirable  to  regulate 
absolutely  the  amount  of  nutrients  consumed  in  the  daily  ration? 
729.  What  is  the  general  tendency  as  to  quantity  of  food  and 
amount  of  nutrients  consumed?  730.  Why  do  people  of  sedentary 
habits  require  a  different  dietary  from  those  pursuing  active,  out-of- 
door  occupations? 

CHAPTER   XVIII 

RATIONAL  FEEDING  OF  MAN 

731 .  What  is  the  object  of  the  rational  feeding  of  man  ?  732.  On 
what  is  it  based?  733.  How  does  it  compare  with  the  rational  feed- 
ing ot  animals?  734.  What  is  a  standard  ration?  735.  How  is  it 
determined?  736.  To  what  extent  may  the  nutrients  of  a  ration 
vary  from  the  standard?  737.  How  do  you  combine  foods  to  form 
a  balanced  ration?  738.  What  foods  are  valuable  for  supplying 
protein?  739.  What  foods  supply  fats?  740.  What  foods  are  rich 
in  carbohydrates?  741.  What  other  requisites  should  a  ration  have 
in  addition  to  supplying  the  necessary  nutrients?  742.  Why  is  it 
necessary  to  consider  the  caloric  value  of  a  ration?  743.  If  a  ration 
contained  an  excess  of  carbohydrates  and  a  scant  amount  of  protein, 
how  could  it  be  improved?  744.  How  do  you  calculate  the  nutrients 
in  a  fraction  of  a  pound  of  food?  745.  Give  the  amounts  of  the 
common  food  materials,  as  potatoes,  bread,  butter,  milk,  and  cheese, 
ordinarily  combined  to  form  a  ration.  746.  To  what  extent  may 
foods  differ  in  composition  from  the  average  analysis  given? 
747.  What  foods  are  subject  to  the  greatest  and  what  foods  to 
the  least  variation? 

CHAPTER   XIX 

WATER 

748.  Why  is  water  regarded  as  a  food?  749.  Does  it  enter 
chemically  into  the  composition  of  plants?  Of  animals?  750.  In 


REVIEW    QUESTIONS  347 

addition  to  serving  as  a  food,  why  is  water  necessary  for  life  pro- 
cesses? 751.  In  what  ways  may  water  be  improved?  752.  What 
are  the  most  common  forms  of  impurities?  753.  What  are  the 
mineral  impurities  of  water?  754.  What  is  their  source  ?  755.  What 
effect  do  some  of  these  minerals  have  upon  the  value  of  the  water? 
756.  What  causes  some  waters  to  dissolve  limestone?  757.  What 
are  permanently  hard  waters?  758.  To  what  is  temporary  hardness 
in  water  due?  759.  What  is  the  best  way  to  remove  mineral  matter 
from  water?  760.  What  are  the  organic  impurities  of  water? 
761.  What  are  the  sources  of  the  organic  impurities?  762.  What 
change  does  the  organic  matter  of  water  undergo?  763.  What  be- 
comes of  the  nitrogen  of  the  organic  matter?  764.  What  does  the 
presence  of  nitrates  in  water  indicate?  Nitrites?  765.  What  is  the 
total  solid  matter  of  a  water,  and  how  is  it  obtained?  766.  Define 
the  terms  free  ammonia;  albuminoid  ammonia.  767.  What  does 
the  presence  of  chlorine  in  a  surface  well  water  indicate?  768.  Ex- 
plain natural  purification  of  water.  769.  Can  natural  purification 
always  be  relied  upon?  770.  Why  does  the  character  of  the  drink- 
ing water  affect  health?  771.  What  diseases  are  mainly  caused  by 
impure  drinking  water?  772.  With  what  materials  in  water  are  the 
disease-producing  organisms  associated?  773.  Why  should  a  water 
of  questionable  purity  be  boiled?  774.  State  how  the  boiling  should 
be  done,  to  be  effective.  775.  Why  should  boiled  water  receive 
further  care  in  its  storage?  776.  What  effect  does  improvement 
of  the  water  supply  of  a  city  have  upon  the  death  rate?  777.  How 
may  connections  between  cesspools  and  surface  well  waters  be 
traced?  778.  What  impurities  do  rain  waters  contain?  779.  Ex- 
plain the  workings  of  the  Pasteur  and  Berkefeld  water  filters. 
780.  Why  must  special  attention  be  given  to  cleaning  the  water 
filter?  781.  Explain  the  processes  employed  for  the  removal  of 
mechanical  impurities  of  water  by  sedimentation  and  the  use  of  chem- 
icals. 782.  Why  should  such  purification  be  under  the  supervision 
of  a  chemist  or  bacteriologist?  783.  What  effect  does  freezing  have 
upon  the  purity  of  water?  784.  Why  are  precautions  necessary  in 
the  use  of  ice  for  refrigeration?  785.  What  are  mineral  waters? 


: 


348       HUMAN    FOODS    AND   THEIR   NUTRITIVE    VALUE 

786.  How  are  artificial  mineral  waters  prepared?  787.  What  are 
the  more  common  materials  used  in  their  preparation?  788.  Why 
should  mineral  waters  be  extensively  used  only  by  the  advice  of  a 
physician?  789.  What  are  some  of  the  materials  used  for  softening 
water?  790.  Which  are  the  least  objectionable  of  these  materials? 
791.  Which  are  the  most  objectionable?  792.  What  can  you  say 
of  the  use  of  ammonia  and  ammonium  carbonate  for  softening 
waters?  793.  In  washing  clothing  after  contagious  diseases,  what 
materials  may  be  used  for  disinfecting?  794.  Why,  in  softening 
waters  for  household  purposes,  must  caustic  soda,  potash,  and  bleach- 
ing powder  be  used  with  caution?  795.  Why  is  it  necessary  to 
determine  by  trial  the  material  most  suitable  for  softening  water? 
796.  What  advantage,  from  a  pecuniary  point  of  view,  results  from 
the  improvement  of  the  water  supply  of  a  community  ? 


CHAPTER    XX 

FOOD  IN  ITS  RELATION  TO  HOUSEHOLD  SANITATION  AND  STORAGE 

797.  What  are  the  compounds  usually  determined  in  a  food 
analysis?  798.  Does  such  an  analysis  necessarily  indicate  the 
presence  of  injurious  compounds  ?  799.  What  are  the  sources  of  the 
injurious  organic  compounds  in  foods?  800.  Why  is  it  necessary 
to  consider  sanitary  condition  as  well  as  chemical  composition? 
801.  What  are  the  sources  of  contamination  of  foods?  802.  What 
is  the  object  of  the  sanitary  inspection  of  food?  803.  How  may 
flies  carry  germ  diseases  ?  804.  Why  should  food  be  protected  from 
impure  air  and  dust  particles  ?  805.  Why  should  places  where  vege- 
tables are  stored  be  well  ventilated?  806.  How  may  the  dirt  ad- 
hering to  vegetables  be  the  carrier  of  germ  diseases?  807.  Why 
should  the  cellar  in  which  food  is  stored  be  in  a  sanitary  condition? 
808.  What  effect  does  the  cleaning  of  streets  and  improvement  of 
the  sanitation  of  cities  have  upon  the  death  rate?  809.  Name  the 
three  natural  disinfectants,  and  explain  the  action  of  each. 


REVIEW    QUESTIONS  349 

810.  Why  must  dishes  and  utensils  in  which  foods  are  placed  be 
thoroughly  cleaned?  811.  Explain  the  principle  of  refrigeration. 
812.  What  kind  of  ferment  action  may  take  place  at  a  low  tempera- 
ture? 813.  Why  is  some  ventilation  necessary  in  refrigeration? 
814.  What  effect  does  refrigeration  have  upon  the  composition  of 
food?  815.  What  relationship  exists  between  unsanitary  con- 
dition of  soils  about  dwellings  and  contamination  of  the  food? 
8 1 6.  Why  should  special  attention  be  given  to  the  sanitary  disposal 
of  kitchen  refuse?  817.  Name  the  ways  in  which  this  can  be  ac- 
complished. 8 1 8.  How  may  foods  become  contaminated  through 
imperfect  plumbing?  819.  Mention  the  conditions  necessary  in 
order  to  keep  foods  sanitary. 


REFERENCES 


The  following  list  of  references  is  given  for  the  use  of  the  student 
in  case  additional  information  is  desired  upon  some  of  the  subjects 
discussed  in  this  work.  The  list  is  not  intended  as  a  complete 
bibliography  of  the  subject  of  foods.  The  advanced  student  will 
find  extended  references  in  the  Experiment  Station  Record  and  the 
variousv  chemical,  physiological,  and  bacteriological  journals. 

1 .  SNYDER  :  The  Chemistry  of  Plant  and  Animal  Life. 

2.  Minnesota  Experiment  Station  Bulletin  No.  54:  Human  Food 

Investigations. 

3.  CROSS  AND  BEVANS:  Cellulose. 

4.  WILEY  :    Principles    and    Practice    of  Agricultural    Analysis, 

Vol.  III. 

5.  Minnesota  Experiment  Station  Bulletin  No.  74:  Human  Food 

Investigations. 

6.  PARRY  :  The  Chemistry  of  Essential  Oils,  etc. 

7.  U.  S.  Department  of  Agriculture,  Farmers1  Bulletin  No.  142: 

Principles  of  Nutrition  and  Nutritive  Value  of  Food. 

8.  MANN  :  Chemistry  of  the  Proteids. 

9.  Minnesota   Experiment    Station  Bulletin  No.  85  :  Wheat  and 

Flour  Investigations. 

10.    ARMSBY^  Principles  of  Animal  Nutrition, 
n.    SHERMAN:  Organic  Analysis. 

12.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  43  :  Digestion  Experiments  with  Potatoes  and 
Eggs. 

13.  Unpublished  results  of  author. 

14.  U.  S.  Department  of  Agriculture,  Bureau  of  Animal  Industry 

Bulletin  No.  49:  Cold  Curing  of  Cheese. 
35° 


REFERENCES  351 

15.  WILEY:  Foods  and  Their  Adulteration. 

1 6.  Minnesota  Experiment  Station  Bulletin  No.  63:  Miscellaneous 

Analyses. 

17.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  8:  Canned  Vegetables. 

18.  LEACH:  Food  Inspection  and  Analysis. 

19.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  No.  256: 

Preparation  of  Vegetables  for  the  Table. 

20.  U.  S.  Department  of  Agriculture  Year  Book,  1905  :  Fruit  and 

its  Uses  as  Food. 

21.  Handbook  of  Experiment  Station  Work,  1893. 

22.  U.  S.  Department  of  Agriculture,  Division  of  Chemistry  Bulletin 

No.  94 :  Studies  on  Apples. 

23.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  69 :  Fruits  and  Fruit  Products. 

24.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  No.  203 : 

Canned  Fruits,  Preserves,  and  Jellies. 

25.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  27  :  Sugar  Beet  Industry. 

26.  SADTLER  :  A  Handbook  of  Industrial  Organic  Chemistry. 

27.  Minnesota  Experiment    Station    Bulletin   No.   86:    The   Food 

Value  of  Sugar.     The  Digestive  Action  of  Milk. 
^8.    HUTCHISON  :  Food  and  Principles  of  Dietetics. 

29.  U.  S.  Department   of  Agriculture,  Farmers1   Bulletin   No  93: 

Sugar  as  Food. 

30.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  252  :  Maple  Sugar  and  Sirup. 

31.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bul- 

letin No.   1 3,  Part  6 :   Sugar,  Molasses,  Sirup,  and  Confec- 
tions. 

32.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  No.  121  : 

Peas  and  Beans  as  Food. 

33.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  No.  122: 

Nuts  as  Food. 

34.  Maine  Experiment  Station  Bulletin  No.  54:  Nuts  as  Food. 


352       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

35.  California   Experiment   Station   Bulletins    Nos.  107  and    132 : 

Investigations  among  Fruitarians. 

36.  U.  S.  Department   of  Agriculture,    Farmers1  Bulletin  No.  74 : 

Milk  as  Food. 

37.  U.  S.   Department  of  Agriculture,  Farmers1   Bulletin  No.  63  : 

Care  of  Milk  on  the  Farm. 

38.  U.  S.  Department  of  Agriculture,  Farmers1  Bulletin  No.  149: 

Digestibility  of  Milk. 

39.  RUSSELL  :  Dairy  Bacteriology. 

40.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13.  Part  i  :  Dairy  Products. 

41.  U.  S.  Department  of  Agriculture,  Farmers1  Bulletin  No.  131-. 

Household  Tests  for  Detection  of  Oleomargarine  and  Reno- 
vated Butter. 

42.  U.  S.  Department  of  Agriculture,  Bureau  of  Animal  Industry 

Bulletin  No  61  :  Relation  of  Bacteria  to  Flavor  of  Cheddar 
Cheese. 

43.  Minnesota  Experiment  Station  Bulletin  No.  92 :  The  Digesti- 

bility and  Nutritive  Value  of  Cottage  Cheese,  etc. 

44.  LA  WES  AND  GILBERT  :     Experiments  with  Animals. 

45.  U.  S.  Department  of  Agriculture,  Farmers'    Bulletin  No.  34: 

Meats,  Composition  and  Cooking. 

46.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  7  :  Lard  and  Lard  Adulterants. 

47.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  193  :  Cooking  of  Meats  as  Affecting  Digestibility. 

48.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  141  :  Experiments  on  Losses  in  Cooking  Meats. 
See  also  Office  of  Experiment  Stations  Bulletin  No.  102 : 
Losses  in  Cooking  Meats. 

49.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  66  :  Physiological  Effect  of  Creatin  and  Creatinin. 

50.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  162  :  The  Influence  of  Cooking  upon  the  Nutri- 
tive Value  of  Meats. 


REFERENCES  353 

51.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  10 :  Preserved  Meats. 

52.  RICHARDSON,  W.  D.,  Journal  of  the  American  Chemical  Society, 

December,  1907 :  The  Occurrence  of  Nitrates  in  Vegetable 
Foods,  in  Cured  Meats,  and  Elsewhere. 

53.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  182  :  Poultry  as  Food. 

54.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  "No.  85  : 

Fish  as  Food. 

55.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin,  Experiment 

Station  Work :  Digestibility  of  Fish  and  Poultry. 

56.  U.  S.  Department  of  Agriculture,  Farmers'  Bulletin  No.  249 : 

Cereal  Breakfast  Foods. 

57.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  50  :  Composition  of  Maize. 

58.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  305  :  Gluten  Flour  and  Similar  Foods. 

59.  HAMMERSTON  :  Physiological  Chemistry. 

60.  EDGAR:  The  Wheat  Berry. 

61.  Minnesota  Experiment   Station  Bulletin  No.  90:  Composition 

and  Value  of  Grains. 

62.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  101  :  Bread  and  Bread  Making. 

63.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  156:  Digestibility  and  Nutritive  Value  of  Bread 
and  Macaroni  Flour. 

64.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  67 :  Bread  and  Bread  Making. 

65.  University  of  Nebraska  Bulletin  No.  102  :  The  Effect  of  Bleach- 

ing upon  the  Quality  of  Wheat  Flour. 

66.  SNYDER:    Wheat  Flour  and  Bread. 

67.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  126:  Bread  and  Bread  Making. 

68.  LAWES  AND  GILBERT:    Experiments  on  Some  Points  in  the 

Composition  of  the  Wheat  Grain,  of  the  Product  in  the  Mill 
and  Bread. 
2  A 


354       HUMAN    FOODS    AND    THEIR    NUTRITIVE    VALUE 

69.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  5  :  Baking  Powders. 

70.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  2  :  Spices  and  Condiments. 

71.  Food  Standards  :  U.  S.  Department  of  Agriculture.    See  Annual 

Reports  of  the  Association  of  Official  Agricultural  Chemists. 

72.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  21  :  Methods  and  Results  of  Investigations  on 
the  Chemistry  and  Economy  of  Foods. 

73.  U.  S.  Department  of  Agriculture,  Bureau  of  Chemistry  Bulletin 

No.  13,  Part  7  :  Tea,  Coffee,  and  Cocoa  Preparations. 

74.  The  Respiration  Calorimeter:  Year-book  U.  S.  Department  of 

Agriculture,  1904. 

75.  Year  Book  U.  S.  Department  of  Agriculture,  1902  :  Cost  of  Food 

as  Related  to  its  Nutritive  Value. 

76.  See   U.    S.  Department   of  Agriculture,  Office  of  Experiment 

Stations  Bulletins  Nos.  82,  71,  129,  116,  37,  55,  150.     See 
also  other  bulletins  of  the  Office  of  Experiment  Stations. 

77.  CHITTENDEN  :  Physiological  Economy  in  Nutrition. 

78.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  98 :  Effect  of  Severe  and  Prolonged  Muscular 
Work  on  Food  Consumption. 

79.  HENRY  :  Feeds  and  Feeding. 

80.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations  : 

Dietary  Studies  in  Chicago  Bulletin  No.  55. 

81.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  116:  Dietary  Studies  in  New  York  City. 

82.  U.  S.  Department  of  Agriculture,  Farmers1  Bulletin  No.  119: 

Banana  Flour. 

83.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  159:  Digest  of  Japanese  Investigations  on  the 
Nutrition  of  Man. 

84.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  150:  Dietary  Studies  at  the  Government  Hospi- 
tal for  the  Insane,  Washington,  D.C. 


REFERENCES  355 

85.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  149  :  Studies  on  the  Food  of  Maine  Lumbermen. 

86.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations 

Bulletin  No.  143  :  Studies  on  the  Digestibility  and  Nutritive 
Value  of  Bread  at  the  Maine  Experiment  Station. 

87.  U.  S.  Department  of  Agriculture,  Office  of  Experiment  Stations, 

Experiment  Station  Work,  Vol.  Ill :  Wells  and  Pure  Water. 

88.  U.  S.  Department  of  Agriculture,  Farmers'    Bulletin  No.  88 : 

Pure  Water  on  the  Farm. 

89     Mineral  Impurities  in  Water.     See  various  bulletins  of  the  Cali- 
fornia and  New  Mexico  Agricultural  Experiment  Stations. 

90.  MASON  :  Examination  of  Water. 

91.  Department   of  the   Interior,   U.  S.  Geological   Survey:    The 

Quality  of  Surface  Waters  in  Minnesota. 

92.  FUERTES:  Water  and  Public  Health. 

93.  U.  So  Department  of  Agriculture,  Farmers1  Bulletin  No.  124: 

Distilled  Drinking  Water. 

94.  TURNEAURE  AND  RUSSELL  :  Public  Water  Supplies. 

95.  VAUGHAN  AND  Now:  Ptomains  and  Leucomains. 

96.  U.   S.    Department    of   Agriculture,   Bureau   of   Entomology, 

Circular  No.  71  :  House  Flies. 

97.  ELLEN  H.  RICHARDS  AND  S.  MARIA  ELLIOTT:    The  Chem- 

istry of  Cooking  and  Cleaning. 

98.  Dr.   WOODS     HUTCHINSON,   Saturday    Evening   Post,    1908: 

The  Real  Angels  of  the  House. 

99.  HARRINGTON  :  Practical  Hygiene. 

100.  PRICE:  Handbook  of  Sanitation. 


INDEX 


Air,  infection  from  impure,  287. 

pure,  disinfectant,  290. 
Albuminoids,  23. 
Alkaloids,  24. 
Allspice,  202. 
Almonds,  77. 

Alum  baking  powder,  188. 
Amids  and  Amines,  23. 
Animal  and  vegetable  foods,  economy 

of,  250. 

Animal  foods,  digestibility  of,  220. 
Apparatus  used  in  experiments,  301. 
Apples,  49. 

pectose  from,  307. 
Ash,  of  foods,  4. 

elements  of  plants,  5. 
Asparagus,  43. 
Available  energy,  217. 

nutrients,  216. 

Bacteria  in  food,  32. 

Baking  powder,  composition  of,  186. 

cream  of  tartar,  187. 

phosphates,  189. 

alum,  189. 

inspection  of,  191. 

fillers,  191. 

home-made,  191. 

testing  for  alum,  315. 

testing  fo'r  ammonia,  316. 

testing  for  phosphoric  acid,  316. 
Baking  tests,  153-314. 
Barley  preparations,  128. 
Beans,  composition,  71. 

digestibility,  72. 

removal  of  skins,  72. 


string,  73. 

use  of,  in  dietary,  74. 
Beef,  1 01. 

extracts,  no. 
Beets,  41. 

Beverages,  composition,  213. 
Bleaching  of  flour,  155. 
Bolting  cloth,  138. 
Bread  and  bread  making,  158-185. 

leavened    and    unleavened     bread, 

158- 
chemical   changes   during   making, 

i59- 

losses  during  bread  making,  160. 

production  of  carbon  dioxide,  163. 

production  of  alcohol,  163. 

production  of  soluble  carbohy- 
drates, 165. 

production  of  acids,   166. 

production  of  volatile  compounds, 
167. 

production  of  volatile  nitrogenous 
compounds,  172. 

wheat  proteids,  part  taken  by,  169. 

oxidation  of  fat,  173. 

starch,  influence  of,  addition  of,  173. 

composition  of  bread,  1 74. 

temperature  of  flour,  176. 

use  of  skim  milk,  176. 

process  of  bread  making,  177. 

digestibility  of  bread,  178. 

graham  bread,  use  in  the  dietary, 
179. 

white  and  graham  bread  compared, 
180. 

mineral  content  of,  182. 


357 


358 

new  and  old,  183. 

action  of  heat  on,  184. 

different  kinds  of,  184. 
Breakfast  foods,  121—132. 
Broth,  109. 
Butter,  composition,  91. 

digestibility,  91. 

adulteration,  92. 

coloring,  92. 

renovated,  92. 

water  in,  305. 
Buttermilk,  88. 

Cabbage,  41. 
Candies,  69. 
Canned  meats,  118. 

vegetables,  46. 

peas,  75. 

Carbohydrates  defined,  8. 
Carrots,  40. 
Cauliflower,  41. 

Cellars,  storage  of  food  in,  283. 
Cellulose  and  properties,  8. 
Cereals,  121-132. 

preparation  of,  121. 

cost  of,  121. 

value  of,  131. 

use  of,  in  dietary,  131. 

corn  preparations,  122. 

oat  preparations,  124. 

wheat  preparations,  126. 

barley  preparations,  128. 

rice  preparations,  129. 

predigested,  130. 

phosphates  in,  131. 

mineral  matters  of,  131. 

coffees,  210. 
Cesspools,  289. 
Cheese,  92-96. 

general  composition,  92. 

digestibility,  93. 

use  of,  in  dietary,  94. 

cottage,  95. 

different  kinds  of,  95. 

adulteration,  96. 


INDEX 


Chemical  changes  during  cooking,  27- 

3°- 
Chemicals,  use  of,  in  preparation  of 

foods  permitted,  36. 
Chestnuts,  76. 

Chicory,  detection  in  coffee,  319. 
Chocolate,  212. 

adulteration  of,  213. 
Cinnamon  and  cassia,  201. 
Cloves,  201. 

Coal  tar  dyes,  testing  for,  308. 
Cocoa,  210. 
Cocoanuts,  77. 
Coffee,  composition  of,  207. 

detection  of  chicory  in,  319. 

glazing  of,  208. 

substitutes,  cereal,  210. 

types  of,  209. 
Combustion  of  foods,  6. 
Cooking,  changes  during,  27. 

chemical,  27-30. 

physical,  30-32. 

bacteriological,  32. 
Corn,  sweet,  41. 

preparations,  122. 
Cream,  87. 
Cream  of  tartar,  187. 
Crude  fiber  of  foods,  9. 
Crude  protein,  21. 
Cucumbers,  42. 

Dairy  products,  80-97. 

use  of,  in  dietary,  96. 
Dextrose,  64. 
Dietary  standards,  245. 
Dietary  studies,  244-260. 

object  of,  244. 

mixed,  desirable,  250. 

of  families  compared,  253. 

in  public  institutions,  259. 
Digestibility  of  foods,  214. 

of  animal  foods,  220. 

of  vegetable  foods,  222. 
Digestion,  combination  of  foods,  223. 

factors  influencing,  223. 


INDEX 


359 


amount  of  food,  224. 

method  of  preparation  of  food,  225. 

mechanical  condition  of  foods,  226, 

psychological  factors,  230. 

individuality,  229. 
Digestion  and  health,  219. 
Dishcloth,  unclean,  292. 
Disinfectants,  281,  289,  295. 
Drying  of  foods,  2. 
Dry  matter,  2. 

Egg  plant,  44. 
.Eggs,  114-118. 
\   composition,  114. 
';  digestibility,  116. 

cooking  of,  116. 

use  of,  in  dietary,  117. 
Elements  in  foods,  7. 
Energy,  available,  217. 
Energy  value  of  rations,  246. 
Entire  wheat,  145. 
Essential  oils,  15. 

occurrence,  15. 

composition  of,  16. 

food  value,  16. 
Esthetic  value  of  foods,  36. 

Fat,  occurrence  in  food,  12. 
composition,  13. 
physical  properties,   14. 
food  value,  14. 
individual  fats,  14. 
oxidation  of,  during  bread  making, 

173- 
Ferments,  soluble,  34. 

insoluble,  34. 
Figs,  54. 
Fish,  113. 

Flavoring  extracts,  56. 
Flavors,  composition  of,  48. 

occurrence  of,  49. 

food  value,  49. 

Flies,  contamination  of  food  by,  286, 
295- 


Foods,  215. 

digestibility  of,  215. 

mechanical  condition  of,  226. 

palatability  of,  228. 

physiological  properties  of,  228. 

ash  of,  4. 

predigested,   130. 

sodium  chloride  in,  4. 

cost  of,  231. 

market  price  and  nutritive  value, 
231-234. 

composition  of,  234-263. 

comparative  nutritive  value,  231. 

economy  of  production,  250. 

habits,  250. 

notions,  252. 

relation    to    mental    and    physical 
vigor,  258. 

amount  consumed,  262. 

injurious  compounds  in,  284. 

contamination  of,  284,  292. 

sanitary  inspection  of,  486. 

storage  in  cellars,  288. 

infection  from  impure  air,  287. 

utensils  for  storage,  291. 

raw,  27. 

cheap  and  expensive,  252. 
Fruits,  composition  of,  48. 

canned,  54. 

dried,  54. 

canned  and  adulterated,  55. 
Fruit  extracts,  56. 
Fruit  flavors,  55. 


Ginger,  200. 
Gliadin,  314. 

;n,  addition  of,  to  flour,  173. 
it  and  dry,  314. 
properties  of  flour,  151. 

bread,  179. 
in  dietary,  180. 
Graham  flour,  144. 
Grape  fruit,  51. 
Grapes,  53. 


36° 


INDEX 


Heat,  action  on  foods,  30. 
Hickory  nuts,  77. 
Honey,  68. 

Ice,  279. 

Inspection  of  food,  286. 

Inversion  of  sugar,  64. 

Kitchen  refuse,   294. 
Koumiss,  88. 

Laboratory  practice,  299. 
Lard,  106. 

substitutes,  107. 
Legumes,  71-76. 
Lemon  extract,  testing,  307. 
Lemons,  51. 

acidity  of,  305. 
Lettuce,  42. 

Macaroni  flour,  148. 

Mace,  202. 

Malted  foods,  121. 

Maple  sugar,  62. 

Meals,  number  of,  per  day,  248. 

Measuring,  directions  for,  302. 

Meat  broth,   109. 

Meats,  98-120. 

general  composition,  98. 

proteids  of,  99. 

fat  of,  100. 

water  of,  98. 

texture  of,  107. 

cooking  of,   influence  of,  on   com- 
position,  1 08. 

extractive  materials,  no. 

smoked,  in. 

boric  acid  in,  312. 

saltpeter  in,  in. 

canned,  118. 
Melons,  43. 

Microscope,  use  of,  304. 
Milk,  importance  in  dietary,  80. 

general  composition,  80. 

souring  of,  86. 

condensed,  87. 


digestibility,  81. 

sanitary  condition,  82. 

certified  milk,  84. 

pasteurized,  84. 

color  of,  85. 

preservatives  in,  86. 

goat's,  88. 

human,  89. 

adulteration  of,  89. 

prepared,  88. 

formaldehyde  in,  310. 
Mineral  matter,  4. 

in  ration,  5. 
Mineral  waters,  279. 
Miscellaneous  compounds,  16. 
Mixed  nitrogenous  compounds,  25. 
Mixed    non-nitrogenous    compounds, 

16. 
Moisture  content  of  foods,  variations 

in,  i. 

Moisture  in  foods,  how  determined,  2. 
Molasses,  65. 
Mustard,  199. 

testing  for  turmeric,  318. 
Mutton,  103. 

Nitrates  in  foods,  45. 
Nitrites  in  foods,  in. 
Nitrogen  free  extract,  n. 

denned,  n. 

composition,  12. 

how  determined,  12. 

variable  character  of,  12. 
Nitrogenous  compounds,  17. 

general  composition,  17. 
Non-nitrogenous    compounds,    classi- 
fication of,  7. 
Nutmeg,  202. 
Nutrients,  available,  216. 
Nutritive  value  of  nitrogenous  com- 
pounds, 1 6. 

starch,  9. 

sugar,  n. 

nitrogen  free  extract,  n. 

fat,  12. 


INDEX 


36l 


protein,  19. 
amids,  23. 
Nuts,  76-79- 

use  of,  in  dietary,  78. 

Oat  preparations,  124. 
Oleomargarine,  92. 

detecting,  310. 
Olive  oil,  testing,  308. 
Olives,  54. 
Onions,  42. 
Oranges,  50. 
Organic  acids,  15. 

occurrence  in  foods,  15. 

influence  on  digestion,  15. 

use  in  plant  economy,  15. 

production  during  germination,  15. 
Organic  compounds,  classification  of, 

7- 

Organic  matter,  6. 
Oysters,  114. 

Palatability  of  food,  228. 
Parsnips,  40. 
Peaches,  53. 
Peanuts,  76. 

fat  from,  309. 
Peas,  74. 

canned,  75. 

Pectose  substances,  n. 
Pepper,  198. 

Phosphate  baking  powders,  189. 
Physical  changes  during  cooking,  30. 
Physiological  properties  of  foods,  228. 
Pistachio,  77. 
Plumbing,  sanitary,  297. 
Plums,  53. 
Pork,  104. 
Potatoes,  37. 

composition,  39. 

digestibility,  38. 

nutritive  value,  38. 

sweet,  39. 
Poultry,  112. 
Predigested  foods,  130. 
Protein,  composition  of,  19. 


properties  of,  19. 

combinations  of,  20.  ^ 

types  of,  20. 

crude,  21. 

food  value  of,  22. 

amount  of,  in  ration,  246. 
Psychological  factors  in  digestion,  230. 
Pumpkins,  45. 

Rational  feeding  of  man,  261-267. 
Rations,  wide  and  narrow,  245. 

standard,  261. 

object  of,  261. 

examples  of,  264. 

requisites  of,  266. 

protein  requirements  of,  246. 

energy  value  of,  246. 
References,  350. 
Refrigeration,  292. 
Refuse,  disposal  of,  294. 
Renovated  butter,  92. 
Review  questions,  323. 
Rice  preparations,  129. 

Saccharine,  70. 

Saltpeter  in  meats,  in. 

Sanitary  condition  of  vegetables,  45. 

Sanitary  inspection  of  food,  286. 

Sausage,  in. 

Sodium  chloride  in  foods,  5. 

Soil,  sanitary  condition  of,  294. 

Spices,  212. 

Spinach,  42. 

Squash,  45. 

Starch,  9. 

occurrence,  9. 

composition,  9. 

properties,  10. 

food  value,  10. 

influence  of  heat  on,  10. 
Strawberries,  52. 
Sugar,  defined,  n. 

beet,  58. 

cane,  58. 

commercial  grades,  58. 

manufacture  of,  59. 


362 

sulphur  in,  59. 

digestibility  of,  59. 

value  of,  in  dietary,  61. 

adulteration  of,  63. 

maple,  62. 

dextrose,  64. 

Sunlight  as  a  disinfectant,  290. 
Sweet  potatoes,  39. 
Syrups,  66. 

sorghum,  66. 

Tea,  203-206. 

black,  203. 

green,   204. 

composition  of,  214. 

judging  of,  205. 

adulteration  of,  206. 

physiological  properties  of  206. 

examination  of  leaves,  318. 
Toast,  184. 
Tomatoes,  43. 

Underfed  families,  251. 

Vanilla  extract,  testing,  307. 
Veal,  102. 

Vegetable  foods,  222. 
Vegetables,  37-47. 

edible  portion,  47. 

canned,  46. 

sanitary  condition  of,  45. 

digestibility  of,  222. 
Vinegar,  193-197. 

preparation  of,  193. 

different  kinds  of,  195. 

adulteration  of,  196. 

solids,  316. 

specific  gravity,  317. 

acidity,  317. 
Volatile  matter,  6. 

Water,  drinking,  268-283. 
importance,  268. 
impurities  in,  269. 
mineral  impurities,  270. 
organic  impurities,  271. 
purification  of,  272-278. 


INDEX 


analysis,  271. 
and  typhoid  fever,  273. 
improvement  of,  276. 
boiling  of,  276. 

filtration  of,  277. 

distillation  of,  278. 

materials  for  softening  water,  280 

testing  purity  of,  320. 
Water  in  foods,  i. 

how  determined,  i. 
Water  supply,  economic  value,  282. 
Waters,  mineral,  279. 
Weighing,  directions  for,  302. 
Wheat  cereal  preparations,  126. 
Wheat  flour,  133. 

spring  and  winter  wheat  flour,  133 

starchy  and  glutenous,  135. 

composition  of,  136. 

process  of  milling,  136-140. 

patent,  142. 

grades  of,  142. 

composition  of,  143. 

ash  content,  145. 

graham,  145. 

entire  wheat,  145. 

by-products,  146. 

aging  and  curing,  147. 

macaroni,   148. 

color,  148. 

granulation,   149. 

capacity  to  absorb  water,  150. 

gluten,  properties  of,  151. 

unsoundness  of,  152. 

baking  tests,  153. 

bleaching  of,  155.          f 

adulteration  of,  156. 

nutritive  value  of,  157. 

water  in,  304. 

ash  in,  305. 

acidity  of,  313. 

moist  and  dry  gluten,  314. 


Yeast,  action  of,   161. 
compressed,  162. 
dry,  163. 


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